W8 uses less RAM and CPU than 7. W8 boots and closes faster than 7. W8 searches faster than 7 (in my experience, I haven't seen an article about this however).
If you don't like the look of 8, download and change the theme. It's not even that hard, why would you trade off performance for a useless start menu and a generic look? You will probably change the theme in 7, too, so why not 8?
I for one love the simple colors look of 8. I like how everything blends in and is a solid color. I had that type of theme in 7. When it comes down to it, the desktop is the desktop and 8 wins the spec wars. (For all those complaining about bugs- win 8 is new and 7 is not. 7 has had time to iron out the bugs and 8 will come soon enough).