There were a few Rebirth costumes that I liked-- Superman finally had a version of the no-trunks look that I could get behind before they put the trunks back on him, Supergirl's previous costume was a perfectly good classic-style outfit, Jon's costume is a great fit for a Superboy-in-training, I liked that they just went ahead and made Wonder Woman's movie outfit her official costume since I thought that was a great compromise between the old one-piece bathing suit and all the different sets of over-designed battle armor they keep slapping on her, Starfire and Raven no longer look completely ridiculous.......

....and that's about it.