looks like the new OS X 10.6 is now called 10.6 Snow Leopard (ars technica). THAT looks very much like confusing it with 10.5. LEOPARD!! Why no Lion? Also the new 10.5.4 is quite near (testing it atm) and 10.5.3 is the most current Update which fixes some bugs in 10.5.2
Not recommended for musicians are: 10.5.0, 10.5.2 and 10.4.10 because of bugs that affect Firewire, USB or both. You can update freely to 10.4.11 or 10.5.3 (or 10.5.4 etc of course).
Snow Leopard is not really a topic for us users before 2009, same with the features of Snow Leopard. I assume they will show someting on WWDC event 9-13.June 2008 (USA of course).
A keynote will be held by his Steveness, Mr.Jobs himself.
Rumours? A lot: A tablet PC, UMPC, new OS stuff and a new iPhone feat. GPS and HSDPA/3G (UMTS in germany) are quite a good hint. the iPhone 2 is for sure. No idea about new computers and hardware but quite obvious they break with carbon lib in 10.6 which means a lot of apps need to be recompiled – that means: You need to re-update your software again then.