OK, on the technical side*:
Pros:
I like some of the louder sounds. To be honest, I actually like the TWI stock sounds too, they just seem a little low volume even on my system with a 15" subwoofer. As far as which sounds are more accurate, well, I really haven't heard how they would be in real life, so I would be lying if I agreed with the Mutator sounds or TWI stock sounds. HOWEVER, some sounds, especially explosions, do sound better loud and many times, TWI stock explosions are weak.
Weapon handling, I like it. I also like the Classic weapon handling from TWI, they just seem to accomplish the same thing only in a slightly different manner. If I were to join a server with either the Mutator or Classic mode, I would be happy. DO NOT care for stock Realism and Action mode weapon handling.
I really enjoy the dynamic movement. I feel like I am going uphill just by running slower. This is nice since it requires you to think about movement and it seems more realistic than just having one speed for all movement (sprint/walk aside)
The ability to select if you want to keep zoom or not. Some players like no zoom, others like it.
Cons:
The slight freeze when I join a team and go to the Class selection menu. Not sure what it is or why. Does not affect the gameplay, just slows selection down for about five seconds for me.
Sounds. Sometimes it just seems the sounds are louder than stock settings overall. I have to turn up VOIP volume (or sounds down) just to hear people speak. Mostly I would prefer explosions louder than stock, with gunfire sounds only a little louder.
Dynamic movement. Occasionally it feels a bit choppy. By this I mean you can tell when it slows you down going up an incline. But if you get to a more level area for just a second or two, you speed back up until you hit a more severe incline. Its just that the transition doesn't feel super smooth.
* I do not use headphones, but I am using Logitech Z-5500 500 watt Speakers (5.1 Surround sound) with a 15" Subwoofer