I have trouble with heels, I have tried everything and had given up but a few weeks ago I tried a pair of Brian Atwood that has a cushioned insole - I was able to stand for hours!
My DD has a high arch and finds certain brands far more comfortable than others as they give her more support. Prada in general seems to be comfortable for her. I think comfort may depend on the shape of your foot. You have to find the brands that work for you by trying on lots of shoes.
I find that Stuart Weizman works pretty well for me, but I do not always like what is offered. I was surprised recently to find a pair of Coach pumps that are comfortable. Usually that brand is too wide for my foot, so I guess you never know.
they run pretty much true to size...do the M Gemis run wide? narrow? is it TTS? ive always wanted to try....