Adobe's latest release is definitely worth the upgrade.
NICE LITTLE IMPROVEMENTS
You know a software program well when you understand its internal logic, and based on that can guess what it should be able to do. But, it's annoying when those "shoulds" don't WORK. For instance, in the past few versions of Photoshop, you could select multiple layers simultaneously and delete or move them-it was frustrating that you coldn't change all of their opacity settings at once.
But you can in CS5. Adobe has poured engineering resources into fixing such niggling things, and adding new and better features.
Ever notice that when you copy from one file or layer to another, your copied selection appears in a random and useless spot? Now you can go to Edit>Paste Special>Paste In Place, and have it land exactly in its original location. The Crop tool now allows you, as in Lightroom, to see Rule of Thirds or grid overlay when trimming. The default options on the Shadow/Highlight tool are much more reasonable and give you a starting point you might actually keep.
You can now save and close all images with a single click instead of clicking OK to save (or reject) changes for each. You can also save a layered, 16-bit file as a JPEG, and Photoshop will automatically convert it down to 8-bit.