I have heavier soled mtb shoes with the spds. I have some flexier soled lakes that I was going to start using to commute - they were not stiff enough for my longer road biking - feet would go numb. But I figure they would work fine for commuting 8-10 miles round trip. And the sneaker-y look would go better with my regular commute clothes too.
Also - thanks for all the advice and the pictures really helped me. I still haven't decided what to use (maybe spd pedals - the "campus" ones") - but at least now I kind of know what I am thinking about.