W8 boots a lot faster (as in 2 to three times) on my machines then W7, also resume from hibernation seems to have been improved again (just a bit, but closer to XP again).
As I do not use my home tablet during the day, I shut it down at the end of the evening and then like the fast reboot when I am back home.
W8 will run your 'normal' programs as 'normal' programs, e.g. probably no speed improvement there.
The TIP is improved in that it now is not really floating anymore (by default), but W7's version was already better then the stupidly small Vista version.
Yes, sites using flash will require you to go to the desktop version, but I have for example seen IMDb change its preview videos to HTML5 compatible, so there you can stay in the metro IE.
On a tablet I like the gestures and overall touch metro interface.
On a labtop without touch screen not so much, they should implement the gestures on the mouse pad!
On a desktop with a mouse (and no touchscreen) it looks usable again, but I still would prefer the 'start' button back, the gestures are mostly done by normal mouse actions.
Overall: on a tablet (like the Acer W500 I am testing this on) W8 to me is a big improvement over W7.