Since when have SPD's not been considered suitable for the road? The SPD system is one of many cleat systems out there, each with different attributes--there's no one "right" system for everyone.

I've used SPDs on all my bikes since 1995. Before that I had toe clips and straps, and then I got Look pedals on my road bike beginning when they first came out in 1986 or so, and that's just because SPDs hadn't yet been invented as far as I know. Back then, my mountain bike still had pedals with toe clips.

I have worn Shimano MTB shoes while road riding for many years. Just this spring I came across some SIDI road shoes at a good price at a local shop, so I bought them.