I had speedplays on my tri bike, but when I got my Keen sandals and found out how much I love to ride in them- I put the SPD's on my tri bike so I can wear my Keens any time. I can walk in them, too, which is super nice for a super klutz like me.
Sure, it might be "taboo" to some, but who cares? I love it, and if you do- go for it!