I use a circuit height reserve altitude (and 500 foot clearance for obstructions). The benefit for me is that alternates show up green on the map. If you don't set a reserve then green on the map does not tell you whether an alternate is reachable. I watch how the arrival height changes to see how I am doing against polar (and the number of up arrows tells you your % over glide). I don't use the glide amoeba.