I've been running 5 for a few days now. I really resisted installing a new version because 3 sucked so hard.
However, I'm pleasantly surprised with 5. I've been browsing all the skins and plugins on the website...some of them are pretty slick.
I haven't seen the milkdrop plugin...now I
have to find it. I think they skipped 4 because the stigma of being so close numerically to 3, which was complete and utter crap, would have been a beta killer for "version 4."
