Gotta say, I've been reading the Bill S New Mutants Artist Select HC the past few days and am really digging it as a nice companion piece to early 80s Claremont UXM. I'd never read much New Mutants material back in the day, especially the early stuff, but it's almost a consistent voice to what was going on over in UXM at the time. Even some of the X-Men show up time-to-time and help with the NM kids' training.
I know it's a pipe-dream but it would really be cool if one day Marvel released some CC X-Men Omnibus books with the correct reading order between the two series, in one comprehensive giant HC book. At times it's almost like one giant story split across two books. Not that you really NEED to read one vs. the other but subplots go back and forth between the titles. The X-titles were really in a golden age when CC was at his peak!