Commuting on a DH bike is a pain in the ass. I rode mine to uni for a few weeks. Then I realised that by spending a couple of hours getting my XC bike back to rideable condition, I could cut my commute time by about 30%. Which meant 7 more minutes to sleep in. Those 7 minutes are a beautiful thing. A DH bike is the antichrist of commuting options. Even hit up revolve, find some POS XC bike, put on new tires pumped to bursting point and commute on that. The nasty geo, shitty gear changes and various noises will be very forgiveable for that 7 minutes sleep.
Also, if you have vaguely decent DH tires, commuting will kill them. That sound when you get up to decent speed, which kinda sounds like rubber rubbing on something, is infact rubber rubbing on tarmac. You are basically blue grooving the tarmac, which is a waste of time and rubber.