I generally stay away from fast guns-- I grew up in a time that we didn't have guns that overpowered. I'd find it degrading to use a Souizen.
If I would have stayed here back in 2010, there's no way I'd let guns like that on the market. As much as I'd love to nerf them, I can't because people paid good money to get easy wins.
I frown on people who use anything stronger than an M4. At the same time, I consider it a handicap for poor PKers.
Tec9, for the win.