In terms of function, these pinners fulful the same roles as the Paslode IM65 F16 (16 gauge) and IM50 F18 (18 gauge) pinners. deWalt also manufacture an angled 16 gauge brad nailer, the DC618, which is their equivalent to the Paslode IM65A pinner. The general shape and form of the guns is similar to that of the Paslodes, the main differences are that there is no gas cannister casing, the fan/cylinder housing is replaced by a (larger) flyweel/motor/solenoid casing and that the DWs have a substantial metal nose guard of cast allow at the front
I've been using both these pinners for about 3 years now on commercial 2nd fix and shop/bar fitting work, so far without any failures. To me that is significant as I had endless problems with the Paslodes I formerly used. The DWs have a number of advantages over the Paslode-type gas pinners to my mind. Firstly they use standard DW 18 volt XRP-style batteries and chargers so if you already have DW cordless kit you can cut cost by buying bare units (Note: Some of the family of nailers are available in 14.4 volt and 12 volt formats as well but those can be hard to find at a reasonable price, the 18 volt pinners will work on either 12 volt or 14.4 volt DW/Elu batteries but they are awkward to remove from the tool and don't have a very long life although still useful as a stop gap should you need it). Secondly, they don't require gas, and I hate gas. It stinks to high heaven and makes me feel sick when I've had to use it in confined spaces (e.g skirtings beneath staricases, utility cupboards, cellar rooms, etc) - the gas is propane, so the exhaust is toxic. I've also had my fair share of problems with gas cannisters; the "new" cannisters which I bought which were out of date, or leaky, the plastic adaptors on the tops of the cannisters which didn't work, not to mention the fact that you can't get them on a Sunday afternoon when you run out and the fact that they are downright expensive, oh, and the gas doesn't like working when it's really cold, etc. I've had my share of problems with guns, too; igniters which were dirty and required a field strip down and clean of the gun (which means you need to buy and carry a field service kit), the circuit boards which fail and require a return to the service centre, the batteries/guns with blackened (corroded) contacts, etc. All of which can lead to the "Passlode shuffle" where you swap bits around trying to find a combination of gas, adaptor, battery, etc which work. The DW guns get you away from this, reduces your running costs and you can still use Paslode pins if you really want to (although it's easier and a lot cheaper to buy Screwfix's own brand). In terms of battery life I regard the DW life as being acceptable. At least with the DWs you don't have to slide the barrert out when you are not using it to stop it from discharging (which you do need to do with a Passy). Time between trips to the charger seems no worse than it is for the Passy
Now the downsides to DW guns. Firstly they are large and heavy compared to Paslodes. Ths is more of a personal thing. I don't have any problem with the size and weight of these guns but I know others who do. Secondly they won't fire the same range of pins as the Paslode guns; by that I mean that the (16 g) Paslode guns will fire shorter pins - 16 g: DC616 32 to 63mm / IM65 16 to 63mm,; 18g DC608 16 to 50mm / IM50 16 to 50mm. Again I don't find that much of an argument because the sort of stuff I want to fire a 19mm brad through will probably split if I use a 16g as opposed to an 18g one. Thirdly the battery technology is only so-so; I'm no fan of DW's battery technology - the 18 volt XRP batteries are particularly bad at hold partial charge between uses (sometimes several weeks) so when you come to use the guns again the batteries inevitably need to be charged. In my own case the "solution" was to buy an 18 volt 1.3Ah NiCd battery pack which holds charge pretty well when the tool is "in store". It also gives me a bit more durability when using the tools as I always have a spare battery. I suspected that the pinners weren't fullly dischargeing the batteries so I bought an 18 volt cordless drill body only last year and my theory was proven correct. I now swap a "spent" battery from the pinner into the drill to "use up" before being charged and this seems to give me a better charge which lasts longer on the pinner
So what are they like in use? Well, once you get used to the weight they're not bad. Both guns have a belt hook to help you carry them. Just make sure that your belt is tight enough as the weight will have your kecks down round your knees if you don't!
The guns can be used in bump and sequential modes just like a Paslode and will fire just as quickly IMHO. For softwood, MDF and plywood they are very easy to use, just press down onto the work piece (the nose has a contact safety lock-out, you must press the nose down onto the workpiece to start the motor and disable the safety) and pull the trigger; for thin plywood/MDF/hardboard you do need to remember to dial in the appropriate (lower) power setting; hardwood takes a little more care with the longest pins as there is less power driving the pin and for that reason I rarely use 63mm pins and stick to 50s or 55s. The guns have a black plastic nose piece fitted (larger then the orange tips found on Paslodes) and come with a spare already fixed onto a bracket on the side of the magazine. These are durable and don't detach that easily; my 16g is on its' second after 3 years whilst the 18g is still on the original. With the DW nose piece on they don't seem to mark any more than a Paslode would. Jams are dealt with by taking the spring pressure off the pin load and flipping open the nose of the magazine, a quick and simple procedure which takes only a few seconds. Pin loading is different between the guns; the 16 gauge gun is loaded by inserting pins from the rear, pulling back the spring-loaded pressure feeder (past the new load) and then allowing it to settle at the back of the pin load; the 18 gauge gun has a magazine where the whole side of the magazine slides back and the loading is from the side. A nice feature of the 18 gauge gun is a visible warning of low pins, but then this magazine is solid steel and you can't see how many pins you've used up. The 18 gauge gun lacks this, but it does have a open lattice magazine structure so it's possible to see directly how many pins you have left. One thing that both guns lack (Paslodes, too, for that matter) is any form of dry fire prevention, which I find a pity as it could save you from occassionally continuing to pin things with "thin air" 
A last couple of features are the yellow headlights (two yellow LEDs either side of the nose) which illuminate the nose of the tool and the mean that working in low light situations is made somewhat easier. These only light up when you press the nose down onto the workpiece. They serve another function in that when the battery is spent they start to flash to warn you that it's time to swap batteries. The other feature is that each gun has a safety lock switch which can be flipped on to stop accidental firing when the gun isn't in use. I think it's more there to deter anyone from fiddling with your gun, but there we have itService and running costs: as might be expected these are pretty low. Batteries fail over time and will need to be reaplaced, probably at about the 4 year mark from what I'm told. At that point I think I'm either going to buy third party batteries (such as those by Tools Down on Amazon or Axminster Power Tool) or possibly build a converted unit to alow me to use my Makita lithiums on these guns. The guns do need to be cleaned and you should try to avoid setting them down on their side where rubbish can get into the flywheels, but other than that it's just been a case of keep 'em clean and a spot of PTFE on the magazines from time to time. I'm told that the actuator mechanisms will eventually go and will cost me about £100 to replace (£60 off eBay). This is a rubber band/spring affair beneath the heavy aluminium casting on the nose of the machine (presumably there for bump protection) and is what drives the anvil. I haven't needed a replacement yet, though, so if/when I do I'll post again
Hope that gives you a good idea about these guns. If you have any questions about them, please ask.
