"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.
Adding features does not necessarily increase functionality -- it just makes the manuals thicker.