I've always had issues with push-up bras. First of all, they tend to be marketed towards small-busted women who want to look bigger, and I find that problematic. Why should we look bigger? Why would we want to? Is there really any benefit in forcing cleavage we wouldn't have otherwise?
This is especially true for me, as I am one of those women who can't create cleavage without also enduring significant pain. I've got wide-set breasts, and these girls require a whole lot of push in order to get anywhere near each other. In the process, I end up with wires poking me in all the wrong places and mattress-like foam padding that makes my breasts all sweaty even in cold weather. I just think it's pointless, and I'm over it.
So why am I writing about this? I've noticed that there are some small-busted women, especially young women, who feel they must wear a heavily padded push-up bra every day in order to look acceptable. It's a body image thing, not a style thing. This really makes me want to shove a bunch of flattering, beautiful, whisper-thin bralettes at them and say: "Wear these, whether you feel okay in them or not, and by the end of the first day you'll realize you're fine the way you are and you deserve to be comfortable. Plus, all women have nipples and it's not a crime if they show through your shirt."
But then I think, well, I don't want to push (see what I did there?) my agenda onto others who don't feel the same way. The only thing I really want to do is gently suggest that you don't actually NEED extra padding or cleavage in order to be attractive. If you like it, and it doesn't make you wish you could just get home already and rip off that monstrosity, go right ahead.
Another thing I want to say about push-up bras is that, depending on the level of padding, you may need a larger cup size. You're not going to get the same extreme cleavage effect if you go up a cup, but the bra may fit better overall, and that's always a good thing.