Really cheap pre-orders and always the lowest prices possible!
I have bought about 70-80% of all my games using OnlineKeyStore and I have never had any major trouble with their service and/or orders. They are always the cheapest place to buy games. I even bought a game once, which I couldn't activate through steam (because it was somehow already activated), and even then their support helped me out and I got a new key for the same product within 10 minutes of tech support.