Should one upgrade - it depends on who you are and what you will use it for.
Having played with the new version and got a feel for the upgrades I sense that this upgrade is doing two things
- bringing back the newbie
- preparing us for the full Adobe integration
I think, for most us developers we will see the filters, drop shadow etc as toys. But for the newbie, it's gee-whiz stuff. Excellent marketing material for the seething masses. Hence the re-appearance of the abc version of the AS panel.
The photoshoppy stuff and Flash Paper are all, IMHO, preparation for a future 'Adobe Suite'. Not that this is a bad thing, one hopes that Flash does not get too laden down with silly toys.
As far as upgrading, it depends what you use Flash for. If, like myself, one has already heavily invested in Sorenson, worked around drop shadows and do most stuff in AS then skipping this upload would not be that detrimental. However if there is a feature(s) that you would estimate save you $300 bucks in time, it is a no-brainer.