I run a 2d on 4s in my buggy and I like it a LOT! It was supposed to be a 2.5d when I ordered it, but some error in marking the box vs the motor got me the 2d. Even geared 46/16 in my Hyper8, temps were good - even at ~55mph.
Now that I've geared to a more reasonable 46/14 (IIRC), it's much more controllable. I love being about 1 foot from a jump and still clearing it with ease.