Bought Win 8 last week on sale at Newegg and just installed to a spare SSD. Install stopped dead for no apparent reason, no matter what I tried. Finally figured out it didn't like having both the iGPU and dGPU enabled in BIOS, installed with no problems after that.
I got used to the new UI pretty quickly, but it's so badly designed I have no use for it. Whoever called it a mobile OS bolted onto a desktop OS was right on the money. Only decent app is Weather, and it got my location wrong.
Bought Start8 immediately, and all is well now. I boot directly to the desktop, and with Administrative Tools and Control Panel set up as menus, I'm all set for real work.
Am I using it as my primary OS? No. When I want to use it, I boot it from the BIOS. Turned off all the Fast Boot options that cause chkdsk to run every time I go back to Win 7, and now I can do a normal shutdown in Win 8 and automatically boot up Win 7. So far I don't see any appreciable performance gains in Win 8, but I haven't played around with DirectX 11.1 yet, so maybe that will make a difference playing videos (I'm not a gamer).
Can't say it was worth the money, but I'm a User Experience designer by trade and really needed to get familiar with it. Maybe when 8.1 comes out I'll switch over permanently, but not now.