Yesterday was my first attempt at Windows 8. I'm not a big fan of change, especially with operating systems. When Vista came out a few years ago, I recommended to all of my clients to wait until the bugs had been ironed out before upgrading. Good thing I suggested that, as Vista was possibly the worst operating system Microsoft have ever made. When Windows 7 came out, the speed and reliability issues are pretty much fixed, and so far with Windows 8, I'm quite impressed. The major difference is the new "Metro" interface. It essentially replaces the desktop and start menu with an Android like tiled interface. If you have a tablet or touch screen, this can be quite useful, as you can put your favourite programs, bookmarks and files in one easily accessible place. However, if you are a fan of "Homeostasis", then check out this guide on making the desktop the first thing you see when you log in.
Something to keep in mind too is that Microsoft have already started phasing out Windows 7. If you want to get a computer with Windows 7, you have about 6-12 months to get it, otherwise your only choice will be Windows 8. Already, I can only source the x64 versions of the software from my suppliers.
Having said all of this, I personally will not be getting Windows 8 for at least a year. As with the previous operating system upgrades, it is extremely wise to wait for all the bugs to be found by other people before jumping in and finding your productivity suffers.