go get it, kids.
not sure about the upgrade path - i received a free upgrade to 3.0 since i bought 2.whatever less than 90 days before 3.0 came out. wmpoweruser.com is saying that the 3.5 upgrade is free to all registered users of 3.0, but i can't find reference to that policy anywhere on SPB's site.
only had a few minutes to play with it so far, but i like what they've done. added more widgets, clarified the distinction between a widget and a shortcut. FINALLY a tasks widget! that's a huge, huge deal for me.