If you are running an x86 tablet with the full version of Windows 8 on it, you will be able to run any piece of software that you can run currently in Windows (assuming you have the hardware for it.
I'm with Matt on this one - I'm actually excited for this new OS and the tablets that are coming. Sure, not a heck of a lot of wizz bang improvements have been made on the desktop, but MS is pulling off (or trying to pull off) a huge shift in direction and capabilities. One of the things I like about the tablets supporting a full version of Windows is that, I write the ordering/viewing/production software for my business and it is web based ... but not online - it runs on local servers. These tablets can run a web server on them and become mobile viewing/ordering tools for me, which I hoped the iPad would be able to do ... but it never lived up to it.
Also, in addition to all the tablet stuff, there are a number of improvements in the underlying OS that are nice to have ... (I've been following the Building Windows 8 Blog for a while now)
A new Task Manager (yeah, not amazing, but a handy feature and definitely about time for an update).
http://blogs.msdn.com/b/b8/archive/2011/10/13/the-windows-8-task-manager.aspxImprovements to multi monitor support (again, not breathtaking, but handy)
http://blogs.msdn.com/b/b8/archive/2012/05/21/enhancing-windows-8-for-multiple-monitors.aspxA new file system (ReFS) which will debut on server and move to the client OS.
http://blogs.msdn.com/b/b8/archive/2012/01/16/building-the-next-generation-file-system-for-windows-refs.aspxIncluding Virtualized Storage in the OS level file system.
http://blogs.msdn.com/b/b8/archive/2012/01/05/virtualizing-storage-for-scale-resiliency-and-efficiency.aspxVastly Improved CHKDisk and disk health handling (this would have saved me a big time headdache earlier this year).
http://blogs.msdn.com/b/b8/archive/2012/05/09/redesigning-chkdsk-and-the-new-ntfs-health-model.aspxFile History (I believe very much like TimeMachine)
http://blogs.msdn.com/b/b8/archive/2012/07/10/protecting-user-files-with-file-history.aspxSupport for VMs built in to the consumer OS.
http://blogs.msdn.com/b/b8/archive/2011/09/07/bringing-hyper-v-to-windows-8.aspxNative Support for reading ISO and VHD files
http://blogs.msdn.com/b/b8/archive/2011/08/30/accessing-data-in-iso-and-vhd-files.aspxAnd then some other improvements to Explorer interface, copying, file collision, etc. Robust USB 3 support, native IPv6 support, secure boot environments, etc.
So, yeah, all of the eye-candyish stuff has been dedicated to Metro and the dual use of the OS on a tablet and PC ... but you still get an improved Windows 7 experience ... and the upgrade is only going to be $40, which is a pretty big drop for and MS operating system.
I think this will be a very big deal for MS. Hopefully they can pull it off. I hope they don't build too big a wall between data from Metro apps and desktop apps - I don't want to be forced to pull up full screen metro apps to check email, look at a calendar, etc. when using the tablet at the desktop docked to other displays. But it would still be great to use those Metro apps when on the go.
As for the start screen ... I won't miss the Start Menu - I don't use it. I pin the few regular applications I use to the task bar, and for the rest I use Launchy (www.launchy.net) - a free, open source app launcher that indexes your applications, allows you to include web shortcuts etc. Much faster than any other launcher I have used.