This worked for me ...
I have a iMac at work, mac book air at home, iphone. All I really wanted was ad free radio at work. (No more obnoxious McDonnalds comercials is worth the $25 to me). Anyway, I had all the issues everyone else is talking about, it scanned some, and hung forever (24 hrs) "sending Info to Apple"
So this is my recipe:
1. Click Stop on teh sending info to apple page.
2. This enabled me to turn OFF itunes match. (Menu Store>Turn Off Itunes MAtch)
3. This enabled a new button on my account page. (Menu Store>View Account(Your_account_here))...
4. Now in My Account>iTunes in the Cloud section I have a new button: Add this computer.
5. Click - wait for it .... POOF! ITs all working!
Don't know if this is a fluke, but seeing how buggy my experience has been with this program, it's worth sharing.
Cheers!