have only just began to read up on the subject, as im planning to run a full suntour drivetrain, but from what i have read there is something like a 0.3mm difference between the spacing on the rear cassette, which didnt matter too much if you ran the shifters in friction mode
http://shimano-suntour-compatibility.blogspot.com/
http://www.sheldonbrown.com/speeds.html
but for the bugger who has dibbed omars suntour cassette, your drivetrain wont work as i have cursed you :twisted: :twisted: :twisted: :twisted: wha ha ha