Whatever you want, without getting in the way.
Give Metro time to mature and develop, and you'll forget all about Win32. You just have to be open to the possibilities a metro-like UI brings to the PC.
I'm keeping an open mind, but to me a single bar with all the notifications I need visible at all times basically. Tiles take up the full screen, and in some cases more than the screen shows. I'm still not sure where the benefit is. I can get all of the things a tile shows in a small gadget or notification bar. I just am not seeing it.