I have cs6. I loveee it, but most of the camera stuff in CS6 you can do in CS5. It just takes more time. Big change for me was the graduated ND filter tool in RAW editor. You can adjust the filter by color temp and tint now, instead of finding a color on the palette board. Other than that, most of the options work a bit faster. Panorama stitching, HDR processing, etc.. those all get a performance boost supposedly.
The other big change I saw was a new lens correction/distortion tool, as well as a new render lighting option. Video editing got a bump too, or so I've been told. But I don't do videos (yet!) so.. no idea about that personally.
I'd download the trial from the adobe website and take it for a test drive!