I hated the size, safety position, trigger, trigger pull, etc.
The grip is overly large for a 9mm with a 15 rd magazine. The whole gun is just bulky on feel too.
Safety is very inaccessible. This becomes a big problem when you are forced (by Army Regulations) to carry it with the safety on. When you rack the slide a lot of people accidentally engage the safety.
Everyone I have shot has absolutely horrible triggers. Tons of creep. No crisp break or reset.
Sights cannot be easily replaced to night sights. And no rail on the M9 either.
Just over all a lot I don't like slapped together in one gun.
They have different models that arent the same as the M9, some of which address your dislikes.
The Vertec models(I own a 96FS) have a straightened backstrap so the grip is much smaller. MecGar(which makes factory mags for Beretta and SIG, among others) makes flush fitting 18 round mags for the 92/M9 series and 20 round mags, where the base plate sticks below the grip about an inch. So IMO, the 15 round capacity is a moot point.
The "G" models are different than the F or FS models in that its a decocker only. The safety lever only decocks the hammer back into DA mode.
As far as the trigger, you can buy a $5 "D" model(DAO version) mainspring and install it in a few minutes. It lightens the DA pull by 2lbs and SA pull by around 1lb.
If you dont like the position of the safety, the Steel-I model features a frame mounted safety, as well as a straight backstrap to reduce the size of the grip. Most of them out there are also SAO.