The H&K design is used by SOCOM as the Mk 23 Mod 0 and marked to the civilian shooters as the USP. Military pistols are designed to take the M4 suppressor made by Knights Armament Co. and are in .45 ACP.
The design is very good. It has rails for the addition of flashlights and other sighting accessories that seem to be the vogue. However, for the average shooter it will mean a heavy $$$ investment before he/she gets the spare magazines for the pistol. H&K magazines are not cheap -- like everything else H&K builds. I think that the average shooter could do as well with a cheaper pistol of a like quality and have money left over for spare magazines and ammunition. The pistol choice would then come down to either a single action like the M1911A1 or a double action like the S&W 4506. After that, it would be the choice between single stack and double stack magazines. The only problem with double stack magazines in 40 S&W or .45 ACP is the grips tend to be uncomfortable for people with smaller hands, especially women.
The .40 S&W cartridge was an attempt to bridge the caliber gap between the 9x19 NATO (.354 bullet) and .45 ACP (.451 bullet). The idea was that the 9mm was very mild in recoil, but lacked stopping power and the 45 was the exact opposite for average shooters. Since police departments and most civilians don't shoot enough to become adequate shots with either a 9mm or a .45, the .40 S&W is a moot point. However, the .40 S&W recoil feels less than a .45.
My reasoning is this: the two most popular handgun cartridges on the planet -- in order -- are (1) the 9x19 NATO (aka 9mm Luger/Parabellum) and (2) the .45 ACP. One usually does not have a problem restocking one's ammo supply with either round. The .40 S&W is an odd ball when it comes to logistics and distribution.