My main door is 18' wide, makes it real easy to get cars in and out, with plenty of room between to swing doors. I don't have to move cars to get the lawn mower out. Its 18' x 8' steel and I use a regular 3/4 horse craftsman opener.
When its cold, its one big uninsulated hole in the wall, and rattles pretty loud on windy days, but my weather stripping is shot or nonexsistant.