I hate roadie spds! (yes I've got em, and I'm used to them but I still hate them)
They're harder to clip in and out of when used with proper carbon soled shoes as you just slip off if you dont get it bang on – not ideal at traffic lights etc.
On the road their efficiency benefits tend to come from stiffness of the shoe/pedal combo. However you can almost replicate this with say, candys and a proper carbon mtb race shoe – which has the benefit of not making you walk like bambi on ice and is easier for frequent clipping in and out.
And look cleats especially seem to be made of cheese – you'll be lucky to get 3 months out of them even if you avoid walking on them.
Personally I reckon that if you're doing a lot of miles, not stopping at traffic lights, won't walk anywhere and want maximum efficiency at the expense of day-to-day useability then roadie spds are fine.
If you want 99% of the benefits with 10% of the feckery factor then get some decent spds and some good stiff mtb shoes… (These figures are advisory only!)