Hi guys, you need to use a Verified PayPal, it both increases your chance of not getting knocked back on verification and should stamp out your credit card issues as OG can't see your card details through paypal.
You should always run a AV, if you don't and you get keylogged, you deserve it really.
OffGamers probably get scammed heaps, WoW keys are valuable, I re-sell them and I get asked to verify again every so often, it's fair enough - you try having hundreds of dollars taken from your paypal account because some un-secure users email got hacked or something, it's annoying.
I purchase from them nearly everyday and all orders are filled for keys within 10 minutes, all gold has been filled within 24 hours, usually with a phone call (even to intl mobiles), the shortest wait for gold i've had was 2hrs.
Their live support is so-so, sometimes you will get a fantastic rep, sometimes they will be useless, make sure you use their feedback thing after you're chat so you can get them fired - or promoted!