The content aware features work very well, though not perfectly. I have only had it for a couple of weeks, so with experience I may find ways of increasing my chances. The features depend upon available content in the image that can replace whatever you need to replace. I would say they speed things up by at least 90% overall. The other 10% is spent in a bit of fine tuning with the standard clone tool or the healing brush which requires you to identify the source. I have also found it useful to use the lasso tool loosely around the detail I am zapping. It is not pure magic, but comes very close.
HDR Pro is superb. It has a ghost removal feature that works very well. HDR sequences shot long in the past, but unusable due to people moving are now sharp and clear. Thank goodness I did not delete them. Selection tools are greatly enhanced. Lens corrections are built into ACR and the main program and work easily. In once case the lens I was using was not in the current database, so it went out and found it, adding it to the database. ACR works very well with JPEGs now as well as RAW. I was able to reinterpret a bunch of early digital shots, done under difficult circumstances with an early digital camera and turn them into a fine web-album. Of course, with 14-bit RAW from my Nikon D700, absolutely optimum image quality can be extracted.
They spent a lot of development time on details, so the overall impression is that everything works better. No longer do you have to reduce the bit-depth manually to 8-bit to save as a JPEG, for example. Put the Measure tool along a line that needs to be vertical or horizontal and click the Straighten button. All these little refinements add up.
Bridge is much improved and much more tightly integrated. Web-portfolio and PDF creation has moved to Bridge, though it can also be installed in Photoshop. For those without the monitor space to have both open, there is now a Mini-Bridge that opens within Photoshop itself.
I skipped CS4 - not intentionally - but just never got around to upgrading from CS3. I guess there just was nothing exciting enough to make me whip out the plastic. Of course, CS5 has everything that CS4 did but has so much more. So much in fact, that it will take me months to be completely fluent in it. There is much that I have yet to even try. By far, the biggest upgrade since I began using Photoshop way back when.