If you REALLY want to try devel apps, the best thing to do is be VERY careful. Don't install a bunch at once (this way you know if something specific has messed up your device) and once you installed what you want DISABLE the repository. That way you won't get untested updates.

The quality of applications is much better once they actually reach testing anyway and if they're good enough they get promoted there pretty quickly. Remember the devel repository is just that; software under development! If the developer doesn't think it's ready for use then chances are, it isn't ready for use.