As luck would have it, my hard drive on my 5 year old Athlon 5600+ home desktop computer crashed. I bought a new hard drive and re-installed Vista from my recovery disks. I wanted to completely update Vista which took over 12 hours (There were at least 4 or 5 times with 20-80 updates) to bring my 2007 vista OS up to date.
I then partitioned the hard drive, bought Windows 8 online and loaded it on the new partition so that I have a dual boot. The Windows 8 install was very easy and fast (less than an hour).
The new start screen with the tiles is awkward to use. First of all, I do not have a touch screen. I'm not sure I will get one; I am not a big fan of fingerprints all over my monitor. I am not sure that a touchscreen is more efficient to than using a mouse. My preference is to go to larger and multiple monitors which necessitates the monitors set farther away from me. Having to reach for the screen and to make large sweeps seems to be less efficient than a traditional mouse. Secondly, the tiles are ugly in my opinion. They are large and plain and remind me of children's megablocks. I actually prefer the aero graphics over the plain Win 8 graphics. I am so used to the icons that you find on old windows, iOS and Android. They seem to float almost 3d like on the screen. On the other hand, the tiles appear very 2D. Thirdly, the interface is not very intuitive and you need to make multiple moves to do what used to be simple tasks. Even if you want to stay in the traditional desktop, Win 8 will direct you back to the tiles. With more time, I may get used to it. But right now, I really do not care for it at all. Finally, the apps are very limited and appear primitive. The bing maps app is very low end.
So far I can tell that Win 8 is a lot smoother and faster than Vista. If you want to get some more life out of a Vista computer, I think it is worth the $40. However, I really did not notice a big difference from Windows 7 in terms of speed or smoothness (compared desktop to desktop, I prefer the familiarity of Win 7). I will stick with Win 7 on my other computers (work and home laptops). I would also hold off on buying any new Win 8 computer unless you absolutely need a new computer. Most do not have touchscreens at this time. Also, I would like to see some of the newer designs (some have screens which can flip over).