Too bad our government/military doesn't follow the same line of thinking.
While I have no problem with the M9, I actually think the P320 does offer some benefits for larger organizations that are sort of moot for private citizens. Namely I am talking about the modularity of the P320 in terms of changing grip frames, slide lengths, and calibers without having to purchase entirely new weapons.
Now unless you live in a very restrictive state that makes new firearm purchases difficult, the caliber conversion and size conversion kits are not overly worth it to me. For the price SIG wants for them for only somewhat more you can get a whole new pistol which is what I'd do personally. But if that cost was spread over a whole agency it might actually be worth going with the kits.
This modularity also allows the purchasing of firing control units and then different frames for soldiers/officers of varying sizes or different slides for different purposes (fullsize for duty, compact/subcompact for more covert missions or in terms of law enforcement maybe plain clothes detectives). Again, as an individual person that won't be as big of a concern.
The frames alone are also rather inexpensive and the firing control units seem pretty robust and simple to remove, so maintenance on these pistols should be fairly easy for armorers.
The P320 is nice but does nothing for me that my Glock 19 doesn't already do just fine.
I found the same was true for me as well. I had a P320 Compact that was nice, but I actually shot the Glock better and faster and the Glock is more compact too.