Lipos are fine, The biggest problem with them is over charging or rather over frequently charging. You can go a few game on one charge with a good lipo but if you keep recharging them at half power then they start swelling, I learned this the hard way, I'm now 3 swollen batteries later and doing it right.

One big bit of advice, if you get a G&P motor, replace the pinion gear. They are the worst out there. I've seen so many strip/blow up after a very low round count that it makes me cry.

Really??
I've been running G&P motors for a long time, put them into 1500rpm/380fps builds, and had an M120 go 3 years and over 200k rounds. I've never seen any issues with the pinion gears.
What gearset are you running?

This G&P pinion gear issue baffles me as well. I run a G&P M160 in my 38+ RPS P90 setup and another M160 in my 32ish RPS VFC SR15. The p90's motor has been going strong for over 2 years now and neither have ever given me an issue. My friend's G&P M16 has chewed through THREE G&P M120 pinion gears! I don't know if it's because the material is weaker in the M120 pinion gears or if the shimming is bad or w/e but the disparity in durability iss shocking!

You know that actually might be it, I'm not sure about the motors that 2 of the guys I play with had strip on them at the last game (I do know they were G&P though) but the gun I put together for greenwolf had a M120 motor, it actually detonated (after maybe 100 bbs) and the shrapnel then destroyed the CA gears in it.

Maybe it's an older version of the motor? I know G&P has atleast 2 versions, were they all white end bells or black?

And how was the motor height? I'll admit they're not HARD pinion gears, it's a soft material. But if you don't have the motor height set properly, I'm sure they could strip easily.