I have RMA'd two things in the last 2 weeks. My graphics card overheated, and I got artifacts in BIOS and DOS, and it wouldn't load windows. After waiting a week for them to realise the XFX 6800 was completly sold out in the UK they sent me a refund, so I got a 7800gt for £35 (plus £88 for a new motherboard.) And my hdd caught on fire, and it is in the post now (bloody seagate being based in Thailand, I would have it now if it was based in the UK.)
I think they have to send you a exact replacement, something better or a refund, not anything worse than what you ordered.
(I have to spend my money on the actual gaming components. And I spent it all on them.)