The drawback to using the built in Random play is that you can get duplicate tracks. There's a plugin available that does the same type of on-the-fly randomizing but keeps track of what's already been played to eliminate duplicates.

I'm running 6.5.1 nightly of November 17th 2006. I've found a bunch of bugs that were introduced with 6.5 that have not yet been fixed. SS currently has a lot of issues building an accurate/complete list of your library - both on initial and update scans. Some of these issues get propagated into Slim's DB and others are run-time only (doing Gallery listing and certain types of sorting in SS doesn't produce expected results).

So far with a software-only environment it seems stable enough and usable. My biggest issue right now if that I've received no news from Slim support about my Squeezebox order since they first mentioned UPS screwed the pooch.