I'm a big fan of the Moving Comfort Maia bra, so when I needed something with more serious compression I decided to give the Fiona a try.  It definitely keeps things in place during spinning and low-impact aerobics - that is to say, it mashes and flattens.  It's not the world's most attractive bra (because of the mashing and flattening), but if you want to minimize movement without paying $60+ this is a good deal.  The size seems to run a little small (40D felt more like a 38D), but once it's on it's pretty comfortable.  The velcro-adjustable straps are a nice touch, and the guava color is quite pretty.  I'd buy this bra again.