Longhorn In-Depth: "The latest build of Longhorn seems to offer a more coherent whole than the PDC release last fall. But it's clear that a massive amount of work is still under way. The 3D desktop needs some serious performance tweaks and WinFS is unbearably slow, even on basic functions. It's all well and good to take advantage of new hardware when it comes out, but Microsoft will be facing a hefty installed base of older systems when Longhorn ships.
However, the 3D desktop will be available in tiers, so users who don't have the hardware to handle a system where each window is a 3D surface can revert to a 2D desktop. We're more concerned about WinFS. While it's very innovative, it's still extremely sluggish. It's more stable than last fall's build, but is in dire need of some serious performance improvements. Not everyone will have high speed RAID 0 or 0 1 arrays on their desktops.
This build did feel more solid overall and was a lot of fun to play with. But users will be looking for value beyond fun factor. If Microsoft can address some of the performance issues we've seen, then we'll feel much more bullish about Longhorn. "