Hi. I've been riding my Trek 4900 Alpha MTB as my commuter bike for the past few weeks. I have a 15K ride to work through the suburbs. My advice is to not use a MTB on a purely pavement commute! I use an over-sized laptop backpack to carry everything. Don't do that either.
So, after doing everything I shouldn't be doing for the past few weeks, I figured I should do some research. I've been researching bikes, tips, and all that for the past month. This forum has been great.
I bought a Gary Fisher Cronus through a LBS and all of the gear I'll need. I was referred to this place by a few hardcore commuters I've met over the past few weeks. At first, the hardcore guys were bewildered by my bike and backpack and statement of "I commute to work on this." Now, they just pity me and say you should get a real bike. So, I did.
I'll put up pics and details when I actually pick up the bike next week. This may be a blessing or not, but I ride past the LBS daily. I fear my bank account balance dropping as I stop in on the way home for that one last thing, or upgrades, or silly stuff because it's just so easy.