the problem was in the implementation. older programs sometimes changed more than 7 registers per scanline and that broke compatibility on some models. the copper has enough time to change 7 registers per scan line with no help other than setup from the cpu.
the problem with sham (sliced ham eg. lowres) was that it was designed for ntsc modes so it didnt work that great for pal.
when i frist found out about al this i thought it was great and downloaded developer docs and stuff on it but i didnt use them a real lot.
these images do look really good, but they cant do gradients very well.
pch was an effort to standardize pallete change stuff across all amiga models and display modes and it works really well. if you can find hamlab you can play around with it really easily because you can try different settings quickly and see how it all works.
