There has been a significant amount of speculation and rumour surrounding the existance of a full desktop experience on Windows 8 devices powered by ARM processors. These are the lower priced tablets that are going to exist in the same market as the iPad and various Android tablets, like those make by Samsung and Asus. Before anyone who hasn't been keeping up with this has a panic, there's going to be a normal Windows desktop on fully-fledged laptop and desktop PCs, but on tablets it makes less sense as a user interface. It's not like you could just take your favourite desktop application that you're running on Windows 7 and put it on a Windows 8 device that's using some SoC (system on chip) architecture anyway - it would need to be recompiled to work with those systems.
The main reason that I don't want the desktop is because I don't want developers, including (especially) Microsoft, to be able to treat the Metro UI as a skin that you can just scratch away to reveal something that they designed 10 years ago. It's not that the 10 year old design isn't perfectly functional on a desktop, but on a device with a touch interface it's going to be fiddly at best.
What I want is for everyone who is developing for Windows 8, especially tablets, to have to think about the user experience using touch. The Metro design language works particularly well for this (some would say to the detriment of the traditional keyboard and mouse user), so for goodness' sake, let's please make sure that it's used consistenly.
I've had far too many experiences in the past, particularly with smartphones, which are in some ways more closely related to tablets than PCs are (which is why Apple and Google have taken the opposite approach to Microsoft), where you have a really nice skin up front, only to find that you're only two taps away from something that looks like my A-Level Computing project in Borland Delphi!