Pros

• Metro looks beautiful
• IE 10 Metro is genuinely quite nice to use, mainly because the really minimalist UI is great to use. For the first time ever, a fullscreen web browser actually works fullscreen.
• The boot loader syncs with multiple monitors.
• The new task manager looks really nice (but feels a little dumbed down).
• When you close the ribbon, the new explorer is very nice. The surround takes up very little space, so more space for files.
• The new login screen looks beautiful.
• All of the new 'restarting', 'loading', 'updating' and 'installing' screens you now get when shutting down and booting up Windows are _much_ nicer then the current ones. With the colours they have used, it also feels very easy on your eyes.
• Metro works pretty well with the mouse; I'm imagining much better then most tablet based interfaces.
• Clicking on an already open Metro app just brings it back, and with the big tiles, this is really nice (hit Start, then click app)
• When it works, it is all lightning fast! and I'm pretty sure the slowdown is due to the threads getting blocked rather then slowdown.

Cons

• Pretty much all of the Metro apps that come bundled suck (especially Socialite), and the rest are useless. Only IE and the Weather app are nice to use, Tweet@rama isn't so bad, but the others are just pointless (and there are two touch painting apps, why?).
• Can't close Metro apps. I imagine it works like iOS, where they are freed up on demand, but when your using it on a desktop it's really odd. Especially when you have a regular app right next to it, which you can close.
• Metro apps start to randomly freeze up once you run more then 2 or 3.
• The Weather app can't remember where I live, and often can't get my location. It's really hit and miss.
• The new Start menu is essentially useless, and even working out how to open it takes about 5 minutes (clicking on Start now switches to Metro, so to open you have to move the mouse into the bottom left corner and touch the sides). Newly installed programs appear on the far right in Metro, whilst the Start menu doesn't list any. Even working out how to turn the machine off requires about 3 or 4 clicks.
• No way to get to system applications, like to see system events or open Powershell, as they don't seem to be listed, anywhere.
• Lots of small bugs with typing in text.
• The Control Panel in Metro is just borked; looks nice but only the first few items work.
• The boot loader takes ages to get into, and if your not booting into Windows 8, it requires the machine to fully restart (and so takes longer). Cold boot times are not fast!
• To login, you have to grab the login screen with the mouse, and move it all the way up. This is awesome the first time you do it, but very annoying by the 10th.
• Your Windows Live image, the one you set in Messenger, is used as your login image. That's awesome, except for the fact that Windows Live heavily compresses the image, resulting in your login picture looking very low-quality and blurry.
• If you connect Windows 8 up to your Windows Live account, your forced to use it when you visit Hotmail. So you can't login to a second account (at least in Metro IE).
• Can no longer press Start, and then type in application, to open an application. Start now switches to Metro.
• All of Metro runs within one screen, which is very limiting on a desktop (especially with multiple monitors).
• Blue screened literally about 15 times : (