From http://docs.xamarin.com/guides/ios/getting_started/installat...
"No iOS simulator on Windows. The iOS Simulator runs on Mac OS X, so it’s necessary to switch to the Mac’s screen when testing on the simulator."
"No iOS simulator on Windows. The iOS Simulator runs on Mac OS X, so it’s necessary to switch to the Mac’s screen when testing on the simulator."
I guess you will be able to use a device from Windows, or something like that. Otherwise it won't make sense to provide iOS support for VS.
Correction - you will need a Mac for the final build of the product. VS will connect through network to this Mac ... Not sure if it makes more sense to just use VS as a glorified C# editor. I suppose if you are a hard core VS user it will be easier to do your development from VS.
Visual Studio basically just talks to MonoTouch on a Mac to do the final build steps, to run the Simulator, etc.