I know how you feel amy. I have posted about this lots and there doesn't seem to be a solution. Basically, you end up with everyone saying "use blocks" or something seriously substandard like that. I know what is causing the sticking.

Your entity is standing straight up like normal when it moves up a slope. Look at your bounding box (hit f11 twice). Notice that when you stick on a slope, a bounding box corner dips below ground? That is causing the sticking.

Decreasing the size of the bounding box alone won't help, the entity will just be pulled down more.

What you have to do is find a way to keep it from touching the ground at all, as stupid as that sounds, I found relief to this problem by decreasing the size of the bounding box so that the bottom cut across the ankles then added the same number that I decreased the bounding box size by to the result of the trace. You will find some sticking on REAL steep slopes because the bounding box still dips below the ground slightly.

P.s: Amy. Notice how there are 2 pages and no real solution? Also, I would like for anyone to show me a game made with this software that successfully implements a good solid 3rd person movement script that works on blocks, terrains, and models without some sort of system that limits the diversity (no gravity, completely flat level surfaces, etc.). The reason why is that it is just too darned hard, and that is the dirty little secret of this software. It seems almost designed to allow you to not produce the game that you want.