Like you mentioned, road shoes are not made for walking for more then 10 metres. So you first have to think what you want to do with your bike. Do you want to get of the bike often to go for a short walk then road shoes are not the way to go. Then SPD or the crankbrother system TrekHawk mentions is the way to go with mtb styled shoes.

However if you want to ride long(er) distances and only get of the bike once in a while to get a cuppa coffee (and use the toilet ofcourse) then your feet are better of with roadshoes (hard soles) and the Look, Time RXS/RXE or Shimano SPD-SL system.

Personally I find the road-pedals/shoes more comfortable then the mtb shoes/pedals.