My pair of the new Shimano SPD sandals, SH-SD66, just arrived. Here are my first impressions and comparisons with the SD65 3 strap sandals.
The new sandals are basically identical to the old ones except they are modified to eliminate the center strap. The sole and footbed appear to be identical except for color.
Topside the leather body is again pretty much identical except for elimination of the center strap and slight trimming of the side panels at the top where the middle strap mounted. The netting under the front strap has been narrowed and a padded tongue under the rear strap that extends to about the middle of the foot, side to side, has been added. On the old SD65 the netting extended across the top of the foot under the front and middle straps. Pull-on loops have been added at the rear of the uppers.
The color of my pair is a much darker brown than the illustration on the Shimano web site.