Personally none, but three riders I ride with and several others I know via the Pearce series etc all broke their 951’s some waiting 6months and one up to 9month for Intense to warranty replace them because Intense couldn’t keep up with the demand for replacement rear ends. I wont start on the Socom i know of that with the Mis-aligned top tube, whose warranty replacements ISCG tabs snaped and then the warranty replacement of that’s chainstays broke.
I dont have much experience of the non DH / FR frames but the M1 / M3 / M9’s were notoriously snappy in the chainstays.
It’s a shame as they ride great and look good, and Intense honour there warranties pretty well, but I couldnt be done with waiting 6-9 months for a replacement.