I use MM as well and love it. Not only does it have great functionality, but is easy on the eyes.
I also bought the lifetime upgrades.
I'll point out 4 pieces of MM that I like best;
1. The Ripper is great. It's fast and I have no problems with funky rips.
2. It's getting much better with the DAP compatibility. I've had a Nomad Zen Xtra, Nomad JB3, Rio Carbon, and Rio Karma. They have all worked well with MM.
3. The library funtionality is awesome. Multiple libraries, easy maintenance, very navigable by any ID3 value.
and finally, after extensive work on my original 5000 MP3 library, has the cleanest Tag Database online. Much better than FreeDB and CDDB.
The one con I have with MM is that it is a resource hog. If you're looking for a slim player and library manager that doesn't eat RAM, I wouldn't say this one is in the top 10.
MM has a pretty good online service as well. If you don't mind DRM, this was the one I chose to go with.