I'm kind of curious how apps will work on Windows 8. Since Win8 will run on ARM CPUs as well as x86, I'm guessing everyone will have to recompile their apps to support ARM as well. It would suck to get a tablet and then find out that it won't run apps that your Win8 PC can run. I didn't get a chance to watch the keynote. Did they address that at all?
Edit: I'm talking about non-Silverlight and non-.NET apps here.
Your old programs will be considered "Classic" programs.
On an x86 machine, you'll have an app called "Desktop" that you can launch. When launched, you pretty much have Windows 7. There, you can run all of your Classic programs.
Windows 8 on ARM will not support Classic applications.
So if you need support for a particular application, you could wait until it's available as a Windows 8 app, or you could just make sure you get an x86 based tablet.