Lipo's are awesome. Plain and simple. Besides, you don't have to get an 11.1v lipo, you can get a 7.4v lipo that offers similar power to a 9.6v NiMh battery. Plus Lipo's are smaller and lighter than thier NiMh counterparts. Lipo's also seem to last way longer out in the field than similar Mah NiMh batteries. Lipo's don't get hot when they charge and discharge like NiMh batteries do either. I would take a lipo over a NiMh battery any day. None of my guns have mosfets in them either, and I have seen no ill effects from lipo use. Lipo's are only bad in the sense that they increase the ROF (11.1v) and every gun is gonna have a part wear out sooner or later, and the 11.1v is only gonna mak that happen sooner ONLY if you're tigger crazy and love to hose through ammo. One thing allot of guys gotta realize is that it only takes ONE bb to get somebody out, not a burts of 20+.
One thing I should not is that I usually run nothing but midcaps, shoot heavier and more accurate bb's, and fire semi auto almost exclusively. For that reason is a huge reason why I love my lipo's so much. The trigger response is unrivaled. I have my KWA SR12 setup with a PDI 210% spring and bore up kit. I haven't even upgraded to an atermarket high torque motor, and my 11.1v 4000Mah lipo gives it some outrageous trigger response. It's so fast that you can't even really hear the motor pulling the spring back at all before the shot is already on it's way.