I've been using M1 for over 20 years. In my very raced turbo Eclipse it was changed every 3500 miles since the oil got dirty quick and with the STI it's got synthetic from the factory and must be changed at certain intervals to keep the warranty in tact.
With my NA '99 4Runner I change it every 8000 miles or 1 year whatever comes first but now that I only see about 4000 miles a year I just change it once a year. I just had to replace a valve cover gasket so I got a good look at the valve train and was impressed by how clean it was at 174,000 miles. I use Puralator PureOne filters too.
With the Focus we have dealer changes for 2 years so I'll just stick with what they put in then I'll go with M1.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch