ok - so I noticed one day that many of the studio versions of my songs had been replaced and/or combined with live songs from other albums by a given artist. Luckily, I had a backup. So I restored a bunch of songs, imported them into my iTunes library and then ran iTunes match again. What it did was reduce my song count by about 300 songs and once again certain studio versions of songs are replaced with live versions, and some songs have disappeared entirely.
Is this how Match is supposed to work? Has anyone else run into similar problems?