Originally Posted by oaxacarider
you might want to keep your current bike as your commuter-errant bike, as you get used to commuting you'll start adding the accesories you need (fenders, lights, sleek tires, etc)
as for a new bike, $1500 gives you a lot of choices, if you happy with your trek, test their road bikes within your budget, main thing is fit. try to get the bike that has the handle bars at the same level or higher than the seat you don't want a handlebar that too low for comfort reasons.
What oaxacarider said. I'd get racks and panniers, ASAP before anything else. As for me, i'm saving up for them, backpack hurts my back :/
Your MTB is fine, about 95% of the people I see commuting are on mtb's. I ride a very old style road bike. That was bought for about $20. Don't really have to worry about it getting stolen (if it gets stolen). Rides like a dream.