I just went clipless as well, and after my first long ride am feeling a bit 'odd' in the feet. I think that my feet are pointed inwards too much. Fortunately, SPDs (and the other types too, I assume) have a large amount of adjustability on the sole.

This link should help you out, it helped me: http://draco.acs.uci.edu/rbfaq/FAQ/8h.3.html

SPDs have about 4 degrees of float, btw, which should be fine for comfort, assuming the cleats are aligned well on the shoe. Read the link well, and start carrying a 4mm wrench so you can make tiny tweaks as you ride.

peace,
sam