I have a Revo, and I couldn't be happier with it, but I'm also looking at the E-Revo. I know that the biggest differance is the chassis, with a few other minor differances (besides the power plant itself). I'm hoping that someone has built/seen/run/owned/ both the converted to electric and the E-Revo, and can give me a bit of advice.
The way I was considering doing the conversion was to take the current (not the to be released on the 27th) version of the 3.3 with reverse, and get a clutch adapter for the 5mm motor shaft. I would keep reverse, (I don't race and I will NOT run any vehicle without reverse) and the mechanical brakes. The advantages to this would be the cool factor of a two speed electric, I can use larger batteries than the E-Revo can fit, and I would have a bunch of spare nitro parts for my other one.
The advantages of the E-Revo would be the simplicity of the whole project. Just slip in a good brushless & ESC and get bashing.
Bear in mind I really don't mind the time spent on this. I work in a machine shop, so I have access to lathes and mills as long as I let my boss play with my toys once in a while. And I know that I will be dropping some $$$ either way.