I in fact use Windows XP with the old Windows 95 interface. It makes the system use just as much resources as Windows 95. The Windows XP interface is in fact much more resource hungry and I've stopped using it. It will be interesting to see new interfaces being developed that use just as less resources on open source versions of Windows XP.
It can take advantage of the new trend toward flat interfaces and outline logos in operating systems (Windows 8 of course), in the new major desktop programs by both Adobe and Microsoft, and online applications (I can only think of Gmail). I also see web sites migrating toward flat colors, reversing the development toward gradients in the middle of the last decade (which Europe and Australia never joined in fact, save some French websites), perhaps following the trend by desktop and online applications (and operating systems). Even Firefox got a logo with less gloss last month. OS X did away with some animations, and I think all animations should be done away with. They just make things slower, disserving the purpose of computers. I regret Firefox's addition of a new tab animation, which just makes things slower. The full screen animation serves a function by showing the the usual menus of Firefox are still available at the top of the screen, but the new tab animation does not. A user sees that the plus button simply adds a new tab. It doesn't have to animate out of the existing tabs for such routine operation as opening a new tab. I think the principle on animations is to use it when it can truly help provide some information (such as the existence of the usual Firefox menus, although out of sight at the top of the screen) or alert on something that is beyond the scope of normal computing (normal error messages don't fit in). But otherwise, animations don't serve any computing purpose.
Microsoft should be applauded for the move toward flatter interfaces in their operating systems. The major desktop environments on Linux are still stuck with the bloated gradient-filled interfaces which also Microsoft spearheaded. Unfortunately, it's one thing to have detail in logos and quite another to have gradients is interfaces. One detracts from performance and the other does not.