I was asleep during geometry class but I still tend to agree with Cornfed. I dont think the angle is a huge factor unless you are really high and the target is very close, in which case you dont need a range finder anyway. If hunting with a rifle in mountainous terrain I can see where it might be valuable on long shots, but in the timber I dont think its a big deal.
I typically range a few trees as yardage markers before the hunt. An easy way to cheat is to simply range that tree at the same hieght you are at rather than at the base, thus eliminating the angle. The distance is usually about a yard difference.
My trusty Bushnell compact 600 finally died after about 7 seasons. I was tempted to get a Leupold with the fancy TBR gizmo but opted for the Bushnell Scout for $100 less. Should arrive from Cabelas before the end of the week.