I've been using a pair of budget UE MetroFi 220s that I have been very happy with - they have been durable, I like their sound signature and they fit and isolate well. I've wanted to jump up just a little bit and considered staying with Ultimate Ears, perhaps a pair of Superfi 5s - these seem to be significantly cheaper than retail:
Basically, any reason to worry? Are they often counterfeited headphones, à la CX300s? Standard eBay things - feedback, multiple buyers - all seems to stack up, but you guys and girls are the experts.
Thanks in advance!