So my opinion on this is an evolving one. I didn't like bras that much pre-HRT, they just felt like sweat traps, but they made me feel better about my presentation. One big issue then was the underwires... Those things can be torture on you depending on your body, for me that was the case, so I cut them out.
Now, and just about 9 months of HRT have made those bras uncomfortable and risky (sometimes they slide off because nothing catches the bottom of my breast) and I had to buy new bras. They feel more comfortable and I forget they are on usually, that is until I start exerting myself to the point of sweating. When that happens the bra feels wayyyy uncomfortable. Since you can see my nips and areolas through my shirt, I kind of have to wear a bra to work and stuff for that reason, sometimes I go bra-less when off work though.
When my breast hurt because I am in a growth spurt, I end up having to wear a bra or they will hurt more. This usually is the case for about 2-3 weeks of any given month.
Either way, at the end of the day, it feels great to take off my bra and stretch my arms!