Faster cold boots, less power usage (and longer battery life if it's a laptop), some serious security improvements, new Explorer, faster file copies... It's a whole new OS, not just a new UI.

I'm having to upgrade my Win XP machine because the new XCom game doesn't run on less than Win Vista.

I only use windows for games so I only tend to upgrade when I find a game that wont work.

Depends if you want to play Metro based games or not. Not sure how many there are and if the ones that exist will play well on a PC rather than tablet.

There's also some performance benefits like faster bootup etc, depends if these are valuable to you or not.

There are certain games that will not run on Windows 8. The only one I've personally run into was Grand Theft Auto 4. I had Windows 8 installed on my desktop, could not get the game to run, and moved back to Windows 7.

I assume this is a temporary thing and that either MS or the game vendor will patch it soon enough.

The trouble with GTA seemed to be in the Securom DRM. With GTA5 on the way and knowing the business Securom operates in, I wouldn't be surprised if a patch never came.

However, all of the other games I've tried have worked with Windows 8 on my laptop. It does make me wonder about the future of companies like Securom in a Windows 8 world.

No.