At least 5.0.3 works (launched it from my SL partition).
Well I have 5.0.3 and works with many bugs like don't let add bookmarks and doesn't reopen last closed tabs completely
Its also the buggiest thing on the OS, it disables typing after a few minutes, doesnt want to load web pages some times, and everytime you skip around in a flash video it starts it as a new download without killing the old one meaning youll end up with a bunch of FLV's being downloaded at the same time killing your bandwidth and having your video stopped on sites that dont allow multiple connections.
i am finding that Safari 5.1 is almost unusable on Lion. It drops all internet connections and i have to use network preferences to reboot if you will just to get it use my wifi everytime.
the bookmark bar doesn't work and on and on. im using chrome and its fast as heck on lion. too many bugs to use lion for everyday right now...
i have the latest developer build of chrome and the latest build of firefox as well and they both work perfectly for me on lion...