Adobe's latest release is definitely worth the upgrade.
MORE POWERFUL HDR
Photographers who wanted to try high-dynamic-range imaging in pervious versions of Photoshop had a lot of learning to do first. And eve then, results usually weren't comparable to those you could get from a good stand-alone HD creation program. In CS4, you have to merge images to create a 32-bit HDR file, then convert it down to 16- or 8-bit for real adjustments. The new version of this tool called HDR Pro, works differently. You can still work in 32-bit mode and convert your image down later. But, you can also do that right in the Merge to HDR Pro dialogue. Set the mode to 16- or 8-bit, then use the adjustment sliders to get a file you like.
The labels on the sliders may be confusing to those new to HDR. But, you can get a nice image even if you don't know the terms Gamma and Radius.
The real power in this tool lies in the Curve panel, where you can bring out all the hidden detail of your merged file. Also important; a new check-box for removing ghosting, which helps eliminate the problems you get when you merge a file in which your subject shifted slightly.
Nothing plagues Photoshoppers more than selection people and moving them to a different background. What trips you up most? The har. CS5's improved Refine Edge tool should make that kind of selection easier.
Refine Edge (or Refine Mask when you're working on a mask rather than a selection), introduced in CS3, is now much better. You can control the areas in which the software evaluates the selection by clicking Show Radius. And then you can run Refine Edge again and it keeps improving.
Even my most successful selections using the tool had to be refined a bit by hand. But, then, with every selection tool I've tried, a little bit of touch-up is usually required.