The instruments sounded fine to me with the exception of the bass lacking attack and definition, but it seemed like there were some "extra" background vocals. I think a lot of folks think they're thickening the sound when they do that but too much is too much in some cases. I'd definitely mix them lower and maybe cut out a few voices. It took my band a month last year to demo about 7 songs at a friend's "studio", and it sounded like shit in comparison to what you did in a few hours. Kudos for that.