I also use MTB pedals and shoes. I am currently using Vuelta Typhoon SPD pedals and SIDI Rampa II shoes and love the combination. I am looking to upgrade the pedals in the future for something with a bit more float but I like the shoes very much. I am also, primarily, a recreational cyclist/commuter and like to be able to walk while I am out on my bike. This is much easier with MTB shoes. The only advantage of road shoes with cyclists like us (ie: rec riders and commuters) are the stiffness of the sole, and even then, only if we purchase shoes with carbon soles (hence alot more $$), which will allow a greater power transfer. I tried road shoes on a test ride and did notice a slight difference, but not enough to offset the inconvenience or additonal cost of road shoes for my type of riding.
Cheers,
Brian