I do have a touch of OD, with my hottest pickups, when turned all the way to fully clean, if I have the drive turned up past about 1-2 o'clock. This tells me the clean isn't fully clean, it still has some drive in there.
With my Ashdown SS amps, the drive is much more noticeable, but they are more mid range focused.
With my Rumble amps, there is more clean headroom, with the more mid scooped voicing. I do run them right about the true flat 10, 2, 2, 10 setting.
With my Ashdown tube amps (CTM30 & Little Bastard/LB30), the drive isn't as noticeable and seem to come on more gradually. I do run these amp at the edge of break-up, so the MGC voice might be buried under the natural voice the amps. As the MGC Drive gets turned up and the Clean is turned down, the drive starts coming forth.
I haven't tested it with my Bassman yet, as it's currently offline, as I do some work on it.