I have SPDs on both my road and mountain bike. I have the A520s on my road bike which give a bigger platform, but are single sided. I have the M920s on my mountain bike. I like the unmistakable sound and feel of clipping in and have no problem clipping out on the loosest setting. They have a little bit of float and I have not had any knee issues.

I tried the Frogs and they were very easy to clip out, but I often found I was not getting clipped in or would unclip when I wasn't wanting to. Very frustrating on off-road uphills!

I like the idea of Eggbeaters for off-road mud-clearing, but like Emily, I could not get my second foot clipped in.

I like wearing MTB shoes for road also for the walk-ability of them. Just found some Sidi Dom Ruby Slippers at a deep discount to go with my new Ruby Expert