When I purchased vinyl, the sound quality was almost always great. Rarely have I purchased a new record with poor sound quality, unless it was some bootleg white label or something like that.
Now that I use Ableton, and purchase digital music from sites like Beatport, DJDownload, etc.... I rarely get any music that actually sounds good to begin with.... MP3, WAV, it doesn't matter.
Obviously, the mastering (or the lack thereof) has completely gone to shit with the advent of digital distribution.
I don't know what everyone is doing, or not doing... or whatever..... but all I can say is.... it SUCKS.
All you producers out there..... your sound quality has gone to shit. Please do something about it.

Seriously, though.... what's the deal? It seems like every single file I download has been compressed/limited to fucking hell, and you can't mix anything without clipping hardcore. I have to reduce gains on many tracks by as much as 5-7 dB just to make them mix without redlining the master. There's no dynamics left. Record a piece of vinyl into the computer, and you get a beautiful wave form.... open a Beatport WAV, and get a solid Blue square wave form. Half the time you can't even see breakdowns, it's been compressed so badly.