You also get great trigger response and ROF with the Marui Pro Light:
http://shop.ehobbyasia.com/tokyo-mar...pro-light.html
It's still an NiMH battery, but it is a LOT better than the stock battery. Plus, you get a reasonably strong light for your pistol, which is really useful indoor.
I'm thinking that it should be possible to replace the NiMH battery inside the pro-light with a Lipo. Although I have yet to do it because even after 5 years, my pro-light still runs perfectly.
Oh, and yes, the pro-light will fit any railed pistol, it works on my hi-capas just fine and doesn't mind the recoil.