I have a Toshiba A665 that I specifically use for my experimenting. Yesterday, I took the plunge and did an upgrade, not a clean install. This is probably not the wisest choice for everyone, but I wanted to try this first.
The Windows Compatibility Advisor Report let me know that Avast wouldn't work and the following would have to be fixed with Windows update....Intel Management Interface, Toshiba Shock Sensor Driver, Toshiba x64 ACPI. I started the install which stopped to instruct me to remove Avast which I did with Revo and then the installation went very smoothly. Everything on the laptop and is working including AntiMalware Bytes, SAS, Firefox, Opera, Foxit, Chrome, Adobe Flash and other stuff. The sound was working and My Documents My Pictures were all maintained. Connecting to the web was no problem. In place of Avast, I got MSE which is running perfectly fine. SAS & MBAM updated w/o issues. WUpdate worked fine as well.
Windows 8 told me which programs I had installed that would slow bootup. My FreeCell and Mahjongg are missing. I'm not sure that I like Metro and navigating around is not intuitive in some places, but so far I am having fun with it. I have to admit that the install was much less painful than I thought it would be. I also am not convinced that the OS is worth moving from a well-running Windows 7 box.
The setup on my laptop was pretty uncomplicated to start with. That might have had something to do with the ease of use in my case. And,I did take a chance doing the upgrade rather than a clean install, but I can fool with that later.