I really can't see any justification, from a gamers perspective, for buying a Radeon 5770 over the 4870. DirectX 11 support is scarce at best, and since this is a technically weaker card, won't all the new DX11 games perform bad on this card anyways? If I were to purchase one of these cards, I'd save the $30-$50CAD and get the 4870 1GB. Being a more expensive card for less performance just seems insane to me, being that I'm strictly a gamer and don't really care for hi-def audio or triple monitors.
I just find it somewhat conflicting that so many people are buying 5770's for "future-proofing" future DX11 games. Just like with DX10, only the upper mid-range to high-end will be able to benefit fully and still maintain good framerates. That's just my opinion though, I'm looking to get a 5850 anyways.