I've got milner HD leaves on my H60 and they were fine on our recent run to the gambia. we were very heavilly loaded and making a bit of progress so they had a fair test. these things are relative though, I've never tried OME and my old springs were totally knackered.
I took spare bushes though as I have heard that is a poly bush fails it just drops out, wheras a rubber one will fail over a period giving you some warning.
TLC H60 (now rather battered!)
1968 morris minor traveller
1990 Landcruiser H60. Full rebuild completed 2014
2012 Hilux, mountain top and bedrug with GG AT2s