I just got my new Veiltail betta today from my LFS, his name is crescendo. I kept a close eye on him for the first few hours after bringing him home, and from the time I put him into the tank it seems he has had issues swimming properly, and looks as if he is gasping for air like he was while he was in the cup. (I decided to rescue him simply because the poor thing looked like he needed out of that cup, even though it was the "cleanest" cup there for the fact that it still had a good bit of crap on the bottom =/) He also flared for a few minutes after I had put him in, too. His gills were a dark violet-red, but because there is red on two of his fins as natural coloring this is what confuses me on the ammonia poisoning.
But anyways, he seems like he's fairly young. Aside from mildly disproportionate fins (that I hope is just because they're still growing and not that he has been stunted from that cup), he SEEMS to have adjusted to his tank. I just don't know if he happens to have any kind of poisoning or not, as it seems like I got him from the very tail end of the store's shipment. I know for a fact they don't change out the water in the cups at all, too if that contributes any.