If it's like this one the advice you've received already is pretty good. Slick or street-friendly tires would be a big improvement. If you like the riding position that's positive but you could add bar ends to vary the riding position and get you leaning a little farther forward. You might even want to consider a drop bar conversion but unless you already have the parts and the knowledge that will run into some bucks. If you're serious about commuting you'll probably want fenders and a rear rack.