A fan of Shimano sandals here, have had the old 3 strap version for may years running SPDs.
Have brought a pair of current 2 strap models which have thinner soles and are more flexible and 190g lighter.
Both are excellent for walking off the bike with strongly curved under toe section, nice intrinsic grip but probably not as good as vibram soles(?), not ideal tread for muddy off road walking.
They are different to each other but no problem with either, a lot stiffer than common "sports" sandals so do need the curved front to roll well when walking.
I ride fixed and geared bikes on then.
I also have had a number of mtb shoes which have more flexible (plastic) soles than both sets of sandals and crap grip on hard surfaces.
For the very cold months I have Shimano hiking boots with SPDs (vibram soles) and find they work well for me, but I have been known to take them off and empty the rain out.
My most rigid shoes are Sidi with speedplay specific carbon soles - superb to ride in but death traps off the bike!