There aren't a boatload of updates to this version of Illustrator, just a select few interesting ones. In addition to performance boosts, Adobe has updated its tracing engine, introduced a new pattern creator tool, added variable-width strokes and the ability to apply gradients to strokes, and tweaked the interface.
http://news.cnet.com/8301-17938_105-57418541-1/adobe-illustrator-cs6-sizzles-more-than-fizzles/
In Illustrator, I use the HotDoor CADtools plug-in, which allows Illy to function like a real CAD program, I use the scale and dimensioning tools everyday, so I don't want to have to upgrade CADtools, so I will most likely stay with CS 5.5 for everything except just PhotoShop, and just upgrade PS.
The big winner is Photoshop, I have been using the beta version for several weeks and I think it is well worth the upgrade. Little things like the new cropping tool make a big difference for me.