For those of you who 'love' i-Tunes you have no idea how crappy it really is (though it does have good 'synch' functions).
In comparison MusicMatch which has been around for years is a much better application and able to scale with bigger music libraries.
Unfortunately as this earlier post shows http://deancollinsblog.blogspot.com/2008/02/musicmatch-begat-yahoo-unlimited-begat.html the MusicMatch founders decided to cash out by selling their user base to Yahoo who then screwed over its user base royally.
They forced users to do a one way upgrade to the Yahoo music player platform (eg you couldn't get back the original musicmatch software) which was sub par and had buggy issues.
Yahoo then turned off functionality for MusicMatch users who didn't upgrade like single track super tagging and recently killed off all disc cddb access entirely.
Even funnier is recently Yahoo 'onsold' the user base yet again to Rhapsody (lol must of been sick of people complaining on their forums).
For the last year I had tried 4 or 5 various alternatives but kept coming back to MusicMatch which even with the reduced functionality was still better than the alternatives until last week...
Check it out and download the free version. It pretty much only took me 2 or 3 days before I realised I was happy to pay for the full version, lol though ominously I paid yet again for the lifetime upgrade option.... again. (inside joke for musicmatch users who said they didn't mind yahoo taking over the product but for those of us that paid for lifetime upgrades we didn't realise that meant downgrades as well).
Love some of the add-ons like remote web browser control (so i can use a laptop to turn up down change song etc my main media pc).
Be aware this is a bit of a steep learning curve in learning how to configure all the options but after you live with it for a few days you'll love it.