Depends on the amount of walking you are doing really. If quite a bit, probably best to wear trainers and use flats with some foot retention. If you're only walking a little, I have some Shimano RT4's and get on with them well, and you don't look too stupid when you're off the bike.
Was sorely tempted by these but held off for now, for all of the reasons listed above
So next question, what in the hive minds opinion is the best or a better option for an all day spd 'casual' trainer if there is such a thing?