the reasons why i would upgrade:

- much better keybed
- aftertouch
- lots of new synth sounds from the Motif XS
- all the 'live' drum kits are re done.
- ability to layer 3 voices

every other category has new and improved sounds but the 5 things I listed above would be the reasons why I would make the change.

If i had a tyros 2 I probably wouldnt do it, but I remember my PSR 3000 and i hated the key feel and the fact it had no aftertouch!

hope this helps?
Nick