I have Elements 4 (just trialled v5 for the sake of nosiness) but I use MC exclusively atm.
The new image related stuff in MC 12, coupled with some creative expression based thumbnail captions, view schemes, auto-import and tagging workflows is really working well for me right now.
I did begin to document the system I'm using here, but I didn't realise how involved it actually was untill I sat down to write it up. The system I use developed across several months and relies upon things such as the filenames themselves as well as a few custom library fields and view schemes. I really should go back and finish that, but I think it will be an 'advanced user' thing only. I'll need to assume the reader knows how to create the necessary fields and schemes, and is able to follow what I've done and apply any tweaks needed for it to fit their own environment.
The monotonous, time consuming part is laying those foundations, but once done, you can forget about them and get on with enjoying your photos. I have "Stacks" and "Version Sets" working with MC!
-marko.