I run an Axial SCX-10 Jeep also. I bought the kit version, built it myself, added a couple custom touches of my own, as well as the basic upgrades. It's a lot of fun drive around the yard, in the woods, on some smaller rock piles, and on the trails. If you're looking for a nice scale 4x4 to do a little of everything, definitely get one, but if you're looking specifically for a hard core rock crawler, I'd suggest you take a look at something else, in the 2.2 sized tire class, or larger. Personally, the scale 4x4 trucks are a lot of fun, and sometimes they are more rewarding to drive. The models with larger tires sometimes make things too easy, if you know what I mean.
The SCX-10 is a popular platform and there is a huge aftermarket of parts available for it. It doesn't need a lot to be a good solid platform. My only suggestions for upgrades are the machined steel gears for the transmission and differentials. I'd also suggest looking at getting some better shocks. The stockers are horrible leakers. Other than that, I have no complaints with mine. I run a 35 turn hand wound motor on a 3S pack, with stock gearing, and it's a blast!
