Yeah they hold up pretty well their body's are pretty much the same material as a tamiya. As far as adding hydros or the servo style actuators to the excavators they work well. Thy aren't as strong as a wedico because their not metal but you can still beat on them.
Also Rc4wd makes a nice excavator for about half the cost of the wedico cat. Here's a link to it, and their are a couple o reviews on it on the forum here. you should check it out.
http://store.rc4wd.com/112-Scale-Ear...15_p_1587.html
--Dan