Smartech have improved from what they use to be especialy in the 1/8 scale buggies and truggies and seam to have fixed a lot of problems that they have had with the gears stripping. I have had the new 1/8 truggy and buggy now for about 12 months now putting about 1 ltr of fuel through them each weekend and haven't had any major problems as far as the drive train goes except for the servos and the orings in the diffs leaking. But one they were replaced with some better quality servos and orings, I haven't had any other problems.
I know the earlier models the gears use to strip out regualy due to poor quality materials used but seams to be fixed in the later models.
As far as as just getting used for bashing they are perfectly fine