Haven't used them online but did have to return something from here that I bought in the US and they were very good customer service-wise. I don't think they will refund postage if you have to return for e.g. a different size. When I sent my necklace back, I decided to insure it on the way and so it cost me the guts of €30 to send it, which was money down the drain. So pick wisely and get the right size now (borrow a ring from the Missus and bring it to a local jeweler to have it sized - be sure that you get a ring that fits the intended finger) and away you go - I'd have no qualms ordering from them at all.
Lucky missus!
Sprite