I have used both slotted cleats (the adjustable, not nail-on kind) with quill pedals and also Look clipless pedals over the years. In the past couple of years, I've been riding almost exclusively with clips & straps with touring shoes (usually Puma Ventoux). I don't feel that I lose much efficiency without cleats. Good touring shoes should have ridged soles to keep them from slipping. I do a good deal of fixed-gear riding on the road, and on steep hills greater than 10%, where I need to pull up hard on the pedals as well as pushing down on them, clips and straps seem to me more secure, with less chance of pulling out than in clipless pedals if I inadvertently twist my foot.
I did the Saratoga 200 km brevet on Sunday (http://www.jjctech.com/brevets.htm) on my 1972 Schwinn Paramount track bike with a front brake and 49x18 gear. I had no problems with my feet at all, using MKS track pedals and Puma Ventoux. When I used Look pedals with Sidi shoes, I often had to take off my shoes several times on long rides because of "hot foot." And I can walk around like a human being again.
Mordecai Silver
NYC