I have the XL and two friends of mine have the X. Only complaint I have about the XL is that the engine will test your tuning skills. Once you have the XL tuned though, the engine is very dependable. Everything is still stock but I've sealed the engine. On my friends X, it's been very dependable for both of them. They've had minor issues like tuning, some minor tranny issues and their one way bearing slipping from a high oil content nitro fuel. I've switched my XL to pull start because the fuel I was using(traxxas 20%) was making the one bearing slip so much that I could not even start it. By switching to pull start and switching to Byrons rtr 20% with 16% oil, I have no trouble starting my engine. Also with the pull start I don't have to charge a battery to start it and I don't have to carry around the roto start in the field. Hope this helps and HPI has awesome customer service along with a factory 2 year warrenty.