Nearly everything in my project studio is rack mounted. Nothing in my listening room is rack mounted. It's principally a matter of space. There's so much gear in the studio that without rackmounting it would take way too much space (not to mention all the power, audio, and midi connection issues). When rackmounting you may have to pay a bit more attention to grounding considerations since some equipment uses chasis ground and others don't (and some provide the option with a switch). But proper grounding practice is always a good idea.
