It can feel strange on a PC. The start menu and apps are designed to take over the entire screen, this is counter intuitive to many of us more advanced users who will have lots of windows open at once. For example, I'd like to look into the apps more, but as they hang around taking up the screen while loading, I tend to dismiss them and then just google everything I need in new tabs. Will be different for everyone I guess.
Yeah the multi-monitor thing makes it seem odd too - I'd like to actually be able to put the whole start menu on my left screen while working sometimes, but that's not do-able. However, it does not allow you to set the system up so that the taskbar is across all screens and icons are shown only the taskbar of the screen they're on, which is quite nice (just what ultramon does). I wouldn't be surprised if it gets quite a few tweaks over the next few weeks