Short answer: It's not perfect.
On some show's it works flawlessly, on others, so-so. On some, it doesn't work at all. It all depends on the source, and as always, YMMV. I find that between the 30 second quick skip and the 7 second 'skip back' navigating through commercials manually when CA isn't working is fast and easy once you get used to it.
In my experience, it seems to work about 70-80% of the time; all depending on what networks your regularly watch. Also, your video signal affects the CA ability; the cleaner the signal, the better CA works, IMO.
*On a positive note, it does seem to be improving with each software update. Hopefully, Alcatraz (the next update) will improve it even more. I'm keeping my fingers crossed, but not too hopeful seeing the next generation 55xx series, will no longer support this feature.