I've vaulted the Monkton Gate once before, but only because I was riding my lightest bike.
To be honest, Old Craighall Road isn't awful for commuting purposes, and after the A6106 roundabout going west is easy via the old railway path to Gilmerton, Roslin, etc., or north via Danderhall, Little France and so on. Going south-west I'd probably just stick to Salters Road and Eskbank Road, picking up the old railway path to Rosewell and Penicuik if needed.