I'm more likely to get Windows 8 for the "under the hood" improvements for my desktop PC and use Metro UI on a tablet. Metro UI is just too dumbed-down for proper desktop use. Just like I wouldn't use iOS on a Mac.
This is about what I'm thinking. I'm pretty much equating the new start menu with my experiences using the Zune media player. When I first fired it up, I thought it would be a great interface for a tablet, but it was far from being the most optimal experience with a mouse. It felt way too floaty to me, and the overly largeness of everything felt like such a huge waste of space. It's better to do more with less, than less with more, no matter how pretty the end results are.
In short, they shouldn't give us the same UI on two devices with vastly different input methods for the simple the sake of homogeneity. They should instead give us one that looks and behaves similarly so you have an easy transition between the two, but with features more tailored to their specific platforms. If you're on a tablet, then the Metro UI is fine as is. But on a desktop, where we have much larger screens at much higher resolutions? Here's what I think would work:
Smaller tiles would make alot more sense to me. 32x32 for app launch icons, bigger ones can be used for your more animated tiles. You should be able to easily separate your tiles into specific groups across the screen for easy access and visual identification. Allow for multiple charms to be docked along the side, such as a twitter feed, a search charm, and a list of your currently active applications. Do it right, and it'd be like the old start menu, your widgets, your gadgets, the launchpad, and mission control all Metro'd up and accessible from a single click of the windows key. Everything I've seen of the current Metro UI shows it's more than capable of handling this. It just doesn't in its current state. It's too focused on the whole touch big stuff on a small screen paradigm.
So yeah. I'm hoping that what we're seeing now is nowhere near the final start menu design, and is only shoehorned in as is so developers can get a feel for how W8 will handle on tablets. In the end, I think the concept of Metro on the desktop isn't a bad one, but it needs alot more tweaking before it'll be a comfortable fit with the Windows desktop.
