Well Telmo, it's not due until October (don't recall them saying early or late Oct), so it could be up to twelve weeks before it hits the market. I don't recall any great detail on the T3 until it was actually shipped. Remember the 'teaser' campaign on that until it shipped?
And, while it may not have the SA2 voices from the T3, it certainly has more SA voices from the T2, and, IMO more importantly, the new Guitar Mode style format, so T3 styles should be even MORE easier to import (they are one of the major roadblocks to T3 import, right now).
There's also a major addition to the available effects, which ought to make a fair difference, too. Oh, and while you could PLAY MP3's on the S900, you couldn't record them. If your stick is already pretty full of MP3's for break music or backing tracks, being able to record in MP3 might make the difference between recording and not recording yourself all the time (not to mention speeding up transfer times to the computer).
The new display ought to make a difference for those that complained that getting the best angle on the S900's screen involved a lot of leaning in (or tilting the whole thing back), too.
If you already have an S900, MAYBE it won't be worth the change (depending on what used S900's go for), but this looks like a no-brainer for any other PSR user out there.
Heck, I'm even tempted myself...