My distance control is very poor on uphill and downhill putts - it is tough for me to "adjust" my speed, and I end up leaving uphill putts very short and blowing downhill putts past the hole.
I don't think the problem is related to green reading - I am pretty good at determining left/right break, and I can generally tell how uphill/downhill a putt is. I just can't get the speed right off the putter.
I think it may be a poor choice of technique: I think about how hard I would hit a flat putt, and then take a bit off or add a bit (ie, "I'll hit in 10% harder). That's probably a poor approach, right? I realized - after a particularly bad round on hilly greens today - that it might be better to putt to a shorter (for downhill putts) or longer (for uphill) target instead...basically, imagine a hole that is a certain distance closer/further than the real one and putt to that point.
Interestingly, my approach DOES work pretty well for adjusting to fast/slow greens, but that's something that is generally consistent within a round.