I find myself using a combination of Gearshift and changing the project properties from HDV to DV resolution when working with M2T files on my lowly P4 3.06 system. This works quite well but requires constant adjusting of the properties. It seems to me that if Gearshift included an option to change the project properties to DV widescreen resolution and back again to HDV when "shifting gears", that that would allow for smoother editing on humble systems like mine.