I picked up the re-mastered Megadeth album "Rust in Peace" a few years ago because I was curious about how it sounded. I ended up giving it away to a friend. I prefer the original mix because that's the mix I fell in love with. The re-master is more "in your face" and clearer but I don't feel like it has as much dynamic range as the original mix.
Supposedly, there's a re-mastered version of the Minor Threat discography. I'm curious to hear if they just made it clearer or if they sucked the dynamic range out of it too.
I'm sure you heard about how awful the Metallica Death Magnetic master was. It's compressed within an inch of its life and clips like crazy. Supposedly, there's a version of most of the tracks that someone ripped from a game (Guitar Hero or Rock Band, I think) that haven't been compressed and don't clip. The difference is shocking.