Shooting uphill or downhill is basically the same but it's been my experience that the difference isn't worth thinking about unless you talking about very long distance shots or shots from a very high tree stand. IE: My bow shoots about 1" high at 20yds on a(approx.)25 degree downhill angle. Not worth arguing over that's for sure. The same shots at 30 - 35 yds seem to make me shoot about 3-4" high. Worth considering but still not enough to miss a deer or elks chest area unless you're already off on your yardage estimation.
One of the guys I shoot with has the inclinometer built into his range finder. Mine doesn't. Most times he uses it on steep shot it only registers 1/2 up to about 2yds less to hold at. Again, not enough to cause a miss. More important is proper range estimation.