First, it depends on which sites you visit as some are still incompatible, particularly some banking websites. Also, people have reported problems uninstalling IE7 Beta, as well as issues that started while using IE7 and continued even after reverting back to IE6. It is still a beta so there is some risk involved...it just depends whether or not you're willing to take that risk of losing compatibility and functionality until the glitches can be worked out. I did install IE7 starting with Beta 1 and have only experienced minor issues off and on...nothing to 'ruin the enjoyment of using it,' but there really wasn't much enjoyment to begin with...it is, after all, just an updated version of IE.
Is it safe to use the beta verison of Internet Explorer 7? I know its just a beta version and I would like to try it but are there still alot of bugs that would ruin my enjoyment of using it?