This is a very comfortable bra, but I think I will wind up wearing it more for every day than for the gym.  While it gives very good support, there's not the compression I need for my high-intensity / high-impact boot camp classes.  For the lower impact workouts, or if you have a small chest, it would be fine.  (I'm a 34DD.)  The good news is that since it's NOT one of those super compression max-support bras, it doesn't smash the breasts into a uni-boob.  There's nice separation without cleavage suffocating me.  I will buy more of these.  I'm going to try one cup size up on my next order; they tend to run a tiny bit on the small side.  So if you are normally a full cup I would order one cup size higher than usual.
If I ever find a super high-impact sports bra for large chests that gives separation & doesn't smash my breasts under my armpits or up to my chin, I'm going to buy a hundred of them.  Can it really be that hard to make?

Update:
As a post script to the sizing - I am a full DD cup, which in Mystere sizing is an E.  That's what I wear in their Tisha bra.  After writing this initially I ordered a second bra in a 34F and it fit much better.  The sides come up a little higher so everything tucks in and pushes forward into the cup nicely. That means that the bra shows a little under tank tops or sleeveless blouses, so I mainly wear it when I'm wearing sleeves.  Great support for daily use and my lower impact classes at the gym.