Besides the occasional crash, the most common reports appear to be games whose animation speed, measured in frames per second, suffers under Vista.

Experts blame still-flaky software drivers, Vista's complexity and a dearth of new video cards optimized for Vista's new rendering technology, DirectX 10.

That's despite promises from Microsoft that Vista is backwards-compatible with XP's graphic engine, DirectX 9, and that it will support existing games.

Meanwhile, games written to take advantage of DirectX 10 have been slow to emerge. And one Nvidia executive predicts that gamers may not routinely see games optimized for DirectX 10 until mid-2008.

It's not that bad, says Microsoft