Upload & Sell: On
From a practical standpoint, there are a few things that make 6 worthwhile, but none of them are the things that Adobe might advertise to the public.
As someone who makes a large percentage of his income working daily in Ps, the features that make the biggest difference to me are 5000 pixel brushes, 1000 pixel feathers on selections and a gargantuan 15000 pixel Liquefy brush. Those three alone make it worth the price for me, as they solve hard limitations I was often up against in earlier versions. Almost everything else is fluff, as far as I'm concerned. An improved ACR is nice, but not a world changer for me as I almost always use third party options for raw processing.
For Rusty, the biggest improvement for him moving from CS3 would be full 64 bit and virtually unlimited ram allocation.
The worst thing about upgrading to CS6 is having to deal with the freaking horrible new Crop Tool, which was apparently designed by a tool. Thankfully, you can get most of the older function back by checking the appropriate preferences, but it's still broken as far as I'm concerned.