Well, the moving Speedramps, like those used at TTA are not wheelchair friendly at all, they are too steep. As far as a moving sidewalk, like those at Space Mtn, they can pose a hazzard if the exit from the side walk becomes congested for some reason, like a rain storm and people stopping to put on their ponchos...the folks behind them on the moving sidewalk would come crashing into them.
The ones used to load omnimovers (like the one at Spaceship Earth and the actual load area of TTA) work well, but can also have problems if exiting traffic stops for some reason. Fortunately Spaceship Earth empties into a large building, which cuts down on problems there.