Depends...
To me it was very worth it, because I wanted to switch packages. I originally bought Web Premium CS3 because it was the cheapest available.
This time, it's $599 for any premium package upgrade. So I have three equally priced choices:
Stick with Web Premium, upgrade everything I have, and gain Soundbooth
Move to the design package, gain Indesign, but lose an upgrade for Contribute, which I don't use anyway.
Or the choice I went with. Upgrade to Production, gain After Effects, Premiere, Encore, and Soundbooth. Upgrade Photoshop, Flash, and Illustrator. I don't get upgrades to Contribute and Fireworks, two programs I never use. And I don't get an upgrade to Dreamweaver, which admittedly sucks and will probably cost me $199 down the road, but for After Efects alone I don't mind, as I do filmmaking also. I bought the 3.3 upgrade, so I have Acrobat Pro 9, and get an additional $160 of the CS4 Upgrade price.
The Production Premium upgrade is significant enough that Adobe is raising it to $799 in February, so this is a limited time thing, along with upgrading CS1 or CS2 to CS4 for the same price.