The biggest downside is that you get five extra minutes of bassline, most of which happens at the beginning so that you wonder wtf is being remixed.
I have a lot on me, sometimes just for the campiness, but sometimes they are more fun than the originals. Other times they make a nice companion piece. Or maybe I heard the remixes first and so am more fond of them heh. Goldfrapp's "Ride A White Horse", I had an 8-minute remix of and never even heard the original until months later, and I still can't remember how it goes compared to the remix.
Some songs more easily translate into a dance beat, so they're quite enjoyable. Other times, you really have to warm up to them, if you can at all. I tend to love dance music and cheesiness, so I guess there aren't many remixes that slip through that particular filter.
I'll upload some tunes later for comparison/discussion. Bed time for now!
*E*