We got one for my son who was 8 1/2 last Christmas. He is a pretty tall kid for his age so the bike was a little small for him, but he loved it and still uses it (thankfully since they aren't cheap).
As for how tough, my brother got one for his son last year as well. The boys rode them in some wet weather which is says not to do. My son's bike didn't have any problems. His son's battery started having problems soon after getting the bike. Not sure if this caused it, but Razor sent a new one out. No problems since.
If you can get one at a decent price, I think your son would enjoy it. We got ours at TRU with a % off coupon and GC after spending $xx.
There are a couple models and there is even a 4-wheeler. They also sell them at Dick's Sporting goods around me in Northern VA.
I haven't seen any BF prices on them though. Good luck. Hope this helps.