Poor: HD video playing sucks on oss radeon/linux - on win7/catalyst it's multifold better. I can say the performance is comparable to the Intel IGPs before Sandy Bridge - somewhat like g45 and g41 chips.
Messy: Occasionally I can't connect it with my HDMI. Even when I change/share screens from "1366x768" (my laptop res.) it's not seamless, whereas win7/catalyst manages quite well, adapts as per the display in question.
Is it just me? Or others are having such problems?