I love the kp45. It's my first GBB. I haven't had any experience with any other GBB's. I'm not sure what is the normal amount of shots you can get out of one gas charge, but I can get 1.5 -2 full mags through it before I have to recharge, so I think the NS2 system is quite nice. It fires very smooth as well with a nice kick. I really like it.
I haven't gotten around to getting a drop-leg or anything for it yet. I'm working on getting gear right now. I have it in a pistol holster pouch on my MOLLE vest. It fits fine. It is a bit larger than most pistols though but it's alright.