The FNX is supposed to be an enhancement to the already popular FNP in the sense that it is supposed to answer alot of the "issues" that were reported with the FNP. Things like the grip and some of the internals are enhanced. The overall "upgrades" are minor to say the least, but nevertheless, the FNX is supposed to replace the FNP overall. The internal design is certainly fascinating to me. Each component is made up of several, beefed up components to aid in keeping the platform serviceable on the smallest details and allow maximum strength.
Each rail is removable and interlocks with the unlock block for replacement. Basically all the internal components are designed to come out and be replaced. The only thing susceptible to needing to replace the whole pistol would be the backstrap retention lever. I actually had to have my first FNX replaced due to the lever being corrupted and not holding the backstraps on any longer. I find this to be a huge flaw in the system that they wont use an insertable piece of spring steel instead, so you don't have to worry about compromising the cheap thermoplastic.
The grip is definitely the highlight of the FN pistols that they make nowadays. The grip is slightly aggressive, but it definitely makes it easy to hold onto in all conditions. The grip also maintains a nice and slim figure in both the size grips. I prefer the one with the pal swell since the one that is flat tends to feel flat and a bit awkward, unless you are wearing gloves. Shooting with gloves on is quite simple due to the relatively slim grip as well, even though the trigger on double action is relatively heavy. When getting a good high firing grip, the USP-style decocker seems to be very intrusive and cause alot of discomfort.
The sights on the FNX add a little icing to the cake, which makes this pistol so shootable. It is refreshing to see a pistol that takes a huge front sight and realizes how important it is in order to shoot accurately under pressure and very quickly.
The one issue I have with the sights is the fact that they are basically like Novak sights and are no good for racking the action on a surface one-handed. I really wish that they would have stuck with a sight that was a little more conventional.
The FNX has a character that separates it from most other double action designs when it comes to shooting. I have not and still have yet to shoot a double action pistol like this one. It combines many different factors that give this pistol a sense of being a perfectly utilitarian duty pistol. It comes in lighter than any other pistol in its' size class, but still maintains less recoil than any other pistol with a standard recoil spring. The flat wire recoil spring of the pistol is heavy and seems to keep the recoil down on the pistol, making it a very pleasant shooter.
When I first got this pistol, I spent some time getting used to it, but I soon found it to be easier to use than the USP, which it resembles very much. I feel that for the money, you are getting alot more with this pistol, but I feel that the crappy backstrap system is a definite disadvantage. But if you feel that you wanna preserve the grip, i think you could easily glue the backstrap to the frame. With that, I think this pistol is a slightly better utilitarian pistol overall over the H&K USP in terms of size, capability, and package deal.