I haven't heard of that limitation before, is this true? And not planned for the upcoming update that will already bring cut-paste and other stuff?... If WP7 will not run on dual-core systems at first, that I can really see it substituting Symbian while MeeGo is reserved for more powerful/future devices...
With Windows Phone 7, Microsoft took the Window CE kernel and built a tightly controlled and carefully managed environment around it. Microsoft also rigidly specifies what kind of devices OEMs can build. It must have three buttons, not four. WP7 currently supports just one CPU and one screen size. And WP7 is very much a greenfield site: a large number of features supported by the competition are also missing. The list is pretty daunting.