Definitely replace both servo horns, especially the steering. I never had any problems w/ the drive shafts, I just used a dremel to smooth out the bevel on the inside of the axel cup(someone posted this solution on here) and used heat shrink around the cvds.
I think the weakest point on the buggy is the rear shock tower. The wing stay is only attached to the upper part of the tower, where as most buggies, the lower screws of the wing stay go into the bulkhead. This can cause the shock tower to break if you're prone to casing jumps or doing somersaults.