I have both Shimano M520 SPD and Wellgo WPD-823, I prefer the Wellgo more.
I agree with what have been said so far, going clipless has been one of my favourite upgrades.

For those of you who are planning to commute in clipless, I'd recommend getting a mountain pedal set up. It is much easier to walk in mountain bike shoes than road shoes, and you don't have to worry about grinding out your cleats on pavement. Clipping in and out will become second nature, if you're still worried, clip out before a stop light.

I'm happy to say that I haven't join the Tombay club (0-mph fall) yet.