Chet's response on his blog: D3D and OGL will still be available via command-line flags, just as they are on XP, it's just that D3D (and DX) aren't enabled by default.
More than ever we will really need an API for knowing what pipelines can be enabled - OGL, D3D or plain old software. I suppose by detecting that its a Windows Vista computer we can assume its a recent computer with some kind of D3D/OGL supported graphics card since Vista is graphics-intensive, so we can enable one of those. Yet this still can't be done with WebStart programatically.... but Dmitri T. acknowledges the problem - http://www.java-gaming.org/forums/index.php?topic=14092.15
At least for the OpenGL pipeline I am sure it works fine under Vista if you've a NVIDIA card.
As far as I know ATI hasn't even released own OpenGL drivers for Vista, would be interesting wether the OpenGL-Java2d-pipeline will work with Vista's OpenGL-1.4 emulation.
Gee, tell me more about this emulation - is it D3D emulating OGL?