The Z500+Poulsbo were launched in mid-2008. By then, the driver performance was terrible.
Almost 3 years later, the drivers are still bad and neither Intel, Tungsten or IMG did nothing about it.
What makes you think that will change for the next iteration?
There's already proof of a gigantic change to the better in my former post. Watch the video it's an Intel platform with a 535@400MHz; you don't get such an increase just from twice the frequency. Else see also Exophase's answer.
Exophase,
I'm not 100% sure but I think Tungsten was dropped quite some time ago. No idea though where drivers come from nowadays.