Suposivly the front center drive shaft wears out quickly. If people are putting grease in there like tony said then thats their problem. I haven't had one wear out yet but I use a dry teflon/graphite lubrican't made by Dupont that wont attract any dirt but keeps the parts lubricated. Dirt sticks to grease making parts wear out faster.

I've also heard of bearings in the center diff going bad but again I haven't had that problem yet. I do have the pro kit... I'm not sure if these problems are with the RTR or not.

If you get the 8ight go with the pro kit. You get a much better chassis and shock towers, 2 extra shoes for the 4 shoe clutch (rtr only comes with 2 shoes), metal shock caps over the RTRs plastic ones, an extra set of springs, 2 extra sets of sway bars, diff oil instead of grease, along with your choice of engine and electronics. I'm sure they're is quite a bit more that I'm missing. You will spend more to get the kit together but you have a better package when its done.