I did my research for getting my 4yo his first rc and I wanted something durable and 'hobby' grade so that I could replace the parts for when it inevitably breaks. The adjustable speed is perfect as I can keep it on the lower settings for him and then turn it up when I get to play with it. He's now moved up to the fastest it can go which is pretty darn fast, and has no problem controlling it.
It's been through all sorts of mud, water, rain etc. and hasn't missed a beat. One of the front LED headlights popped out first run but it was easy to put back in and hasn't had a problem since.
Other than the shell which I don't expect to hold up to the abuse we've put it through, it's been near indestructible as evidenced by the video I uploaded (plus it comes with the extra shell anyways which we've had to switch over to). This was the worst hit, but was after many other big crashes at the skate park and it is still working flawlessly. We've only had it for less than a month so we'll see how it holds up, but if something were to break today i'd say we already got our money's worth it's been so much fun and reliable.