MJ isn't like other software - the developers are passionate, attentive to their customers, highly responsive and they move at lightning speed. One of the consequences of such rapid development is that minor bugs and nits sometimes appear in releases made available to customers.
For my money, MJ is the best darn music tool out there - and I am a paid licensee of MusicMatch and several other audio packages. I prefer to participate in the beta program and live with minor bugs, largely because any issues that come up are generally fixed in a day or two (they release daily builds for pete's sake!).
If you are only interested in bug-free versions, I believe MJ v7.2 is still available for download, and it is rock-solid, although it doesn't have the new whiz-bang features that the v8 beta has. If you buy the v7.2 version now, your license will allow you to use v8 as well...