On dirt, they are practically uncontrollable. On grass, they are fun as hell with the right tires.
I run new era's 17mm adapters with 1/8 buggy wheels tires that have really aggressive tires and it gets around great in the grass. I tried running it at an MX track a few years ago and it was like driving on ice. No matter how soft I was on the throttle, constant spin outs made it not fun.
I run 1/8 buggy pro-line road rage tires as well when I'm running at a skate park.
The only downside I have h ad is that when doing big air jumps (excess of 3 feet under it) causes it to bottom out so hard that it breaks the crank case. I got around that by building a damn out of tape around the engine mount, then filled it with jbweld and put the engine in and let it cure. This created a solid footprint for the entire bottom of the engine to rest on and I haven't had an issue since.
Also, the rear shock tower is very susceptible to breaking on bad landings/endo's... I made a roll bar to protect it and haven't had an issue with that since then either.
Keep in mind, I drive mine pretty much like I would my revo. Fast, hard and I jump a lot of stuff the jato probably has no business jumping... but with my mods, it's a tough rig now that is my fastest rig.
I also tried running stampede tires on it... they were completely useless. Not nearly enough weight and it just spun out all the time on pretty much any surface. I was trying to find tires/wheels that would give it more ground clearance to let me run easier in grass as that's the majority of where I run it.
I also made little steel braces for the inner tie-rod mounts as I busted those off a few times. Have not had an issue since I made the braces. Could probably make something similarly out of aluminum, but seemed to get the job done for me.