On my commute bike, I use 2 sided combo pedals with SPD+platforms on both sides like these PD-M424 SPD Dual Platform Pedals
I've tried using clip-on SPD platforms with regular SPD's, and found that those platforms are not very stable, can be difficult to snap in/out, and tend to fall off - they might be ok for a quick trip down the block, but won't stand up to a long commute. Platforms for other clipless styles (like Look) might be more stable, but I like SPD's for commuting since it's easy to walk in (some) SPD shoes.
I also tried some combo pedals with a platform on one side and SPD clipless on the other (I think it was the Shimano M324), and found it too annoying to have to make sure the pedal was flipped around the right way.
So finally I settled on these dual sided M424's, and have been pretty happy, the platform is comfortable for riding with regular shoes and while clipping in to the SPD's took a little practice because of the platform, it now feels as easy as clipping into bare SPD pedals. The SPD part is spring loaded and sticks up a little to make it easy to clip in, but it's not a very strong spring, so it folds down easily with regular shoes. It's not fully recessed under the platform when pushed down so it's possible that would cause some foot irritation on a long ride, but I've never had a problem with it.
When I had a 4 mile commute, I used the platforms with regular street shoes almost exclusively (except for longer rides), now I have a 15 mile commute and use SPD biking shoes almost exclusively (except for shorter rides) and I'm pretty happy with the pedals either way.