I've had to exchange this bra twice now for being too small in the cup. I bought it for the first time in a 32GG, my then-regular bra size, only to find that it gave me some of the worst quadraboob I've ever had. I was willing to concede that a strapless bra running a bit small was to be expected (and as it turns out, I had grown a cup size without realizing it), and I went up a cup size, only to find that the cups still dug into my breast tissue. I exchanged it for a third and final time for a 32HH, which finally did the trick, but there was quite a bit of hoop-jumping to get to this point.
Size issues aside, there's a few things about the fit you can expect: A) If you're not used to padding, get ready, because this bra is gonna amp you up on top. B) This bra is super stiff. Obviously this is necessary because, duh, it's convertible, but if you're used to softer bras with less rigid support, this takes some getting used to. C) The included straps are kind of flimsy, and don't do much in the way of adding support. You can expect pretty much all of the support to come from the bra band even if you do attach the straps.
Other than that, this is a well-constructed bra. I'm not too big on the style (the candy stripes, bow, and button are nice touches, but this just isn't a cute bra no matter how you look at it), but it's sturdy, and it's given me the freedom to expand my wardrobe to clothes I wouldn't feel comfortable wearing without a bra. As long as you take sizing into account, I think this is a great basic convertible bra to have.