Observations after a week of use...
1. More heavily reliant on keyboard shortcuts - if you were used to just clicking on everything from either Start Menu/Taskbar/Shortcuts, it takes some relearning
2. The "hot zones" need improving, particularly with multiple monitors, the Orb or similar needs to make a return to indicate the zone. Zone's should be configurable, e.g. Charms is between monitors and is difficult to find. Would be better if I could configure it to be on my right most monitor.
3. Microsoft Account for UK is not working fully. Limits the apps you can fully use.
Overall, Metro doesn't get in the way, since Windows 7 I've used the Start Menu less for regular applications, preferring the TaskBar and Jumplists.
It takes some time to relearn and modify your workflow, but serious work is done on the desktop and other than a bit of re-learning, over time, I'm actually finding it quite good - the first few days were annoying as hell.
The Metro Start Screen is used for Start->search as before, but also allows me to layout my simple apps so I can just launch those apps when I'm doing something less serious. I think with more apps and some remote control tweaks, it will make a good Media Center front end too.
Not perfect by any means, but MS won't drop it now, so may as well get used to it. I think it needs changes to your workflow/re-learning how you do certain activities, but also time to get used to it. I don't think a valid opinion can be formed after a very short period of time, as it is new and different. I also think that those that embraced the changes in Windows 7 such as pin to taskbar and jump lists will have a much easier transition.