Weston, I have the M540 and have been totally SPD for the last few months. I had the same concerns as you when I was looking at going clipless and I liked the dual-sided engagement. It makes it easier clipping in. As for quick starts, it takes practice. The first time you do it, you'll fall so don't take them for their maiden voyage in traffic. Practice clipping in and clipping out, as well as resting stops and quick starts. Even after a few months, I've gotten much better but I still miss sometimes and I'm sure it looks goofy as hell.

What I usually do is when I'm in, say, a left-turn lane and I see the light will be turning green in about 5 seconds, I back up the bike a few feet, stand up and clip-in and try to do a sort-of track stand until my light goes green. If I'm back some cars, I typically do this when a car a few up goes off the brakes. Like I said, it takes some practice.

My only regret with going with the double-sided pedal is that I now HAVE to take my SPD shoes with me everywhere. The grocery store, Church, etc... I can either go shoeless at my destination or bring a spare pair of shoes with me for my arrival. I'm happy with my purchase but it does have draw-backs.

Unfortunately I can't give a direct comparison between the SPD pedals like the Shimano M540 and a road type SPD pedal.