For me, I really love the new Safari and the improvement of boot time and the computer turn off time. Can you imagine that you only take five seconds may be ten to shut down your computer ? You will never experience this in Windows !
Besides, it is a true 64bits OS ! Unlike, Windows 7, you are really using a 64bit OS and some applications. If you used 64bit Windows 7 with 64bit IE, you will find that something you can't do in 64bit IE. It needs you to use 32bit IE to do it. It sucks !
Do you update your Mac OS ?