I'll respectfully disagree with the advocates of SPD. I started out with SPD's and then started using SPD-SL on my road bike but after riding with a guy who was using Crank Brothers I noticed he seemed to clip in and out so much more effortlessly than I was. After the ride I asked him about them and he too had started with SPD's and urged me to invest in a set of CB pedals.

I did and no how them on my road and trail bikes. The only way I'd try any other system is that if it was cost free. I find the CB to be so much simpler to clip in my cleats and have never had a problem unclipping. The Crank Brothers cleats will fit SPD shoes but the cheapest Crank Brothers pedals are more expensive than the lower costing SPD pedals.

What makes the CB pedals work better is that you just slide forward to clip in due the having a platform and the retention system is 4 sided and rotates.

I recommend the Crank Brothers all the way.