Got one of these for my nephew for christmas too. Like everyone else is saying assembly was pretty easy, in fact the one I bought came with a few extra parts, a couple extra washers, an extra wheel bushing, and a few extra screws. Instructions looked like they were translated from chinese but were comprehensive enough to easily understand.
The toy rides and works well for my nephew but the remote feature DOES NOT WORK AT ALL. Which isn't a big deal IMO, as long as the toy its self works and he can drive it around. As also said the toy is pretty quick and you'd need to be in decent physical health to keep up with it on foot. My brother and his wife don't like the music tones but they can get around that with the audio input jack.
All in all, it's not the greatest quality but for the price listed here on WOOT it's worth it IMO.