I was once a broke student who had a pretty big iTunes collection -- most of it... uhhh ripped from CDs (my own and borrowed*). Today, I'm more than happy to buy all of my music and with iTunes 11 putting the store directly in line with our own music collection, I'll likely be buying more.
I got iTunes Match to "legalize" all of my college days collection. It gave me an opportunity to patch up all my songs, upgrade them to iTunes Plus quality and treat it as all as "purchased music".
From the studios' standpoint, iTunes Match was an absolute stroke of Genius. Give everybody a chance for a fresh start with all their music now legit (for an annual price) and from then on they'll want it to stay that way. They would have otherwise not have gotten a penny from these so called "pirates".
I'm rediscovering
Albums so I'm finding myself re-buying a lot of those ripped songs in their full albums. My taste in music has also changed so a lot of the crap that I downloaded has sat unplayed for years. I created a smart playlist that shows me those songs so every now and then, I either delete a bunch of them or rediscover songs I used to like. Either way, over time, most of my library is becoming legitimately purchased full albums.
If you got iTunes Match for nothing more than to clean up your library and upgrade it all to 256K, then it's the deal of the century. If you continue to pay the $25 bucks a year to have iCloud access to your entire library (legit and ripped), you're still coming out on top.
*Disclaimer: For legal purposes, all of the above post was pure fiction.