The primary reason Microsoft will always have a strangle-hold on the desktop and Office suite is because they control all the variables in the equation. If a new feature is suggested, they can manipulate everything they need to without a lot of political muss and fuss.
Integration in Gnome usually means a committee/standards body, lengthy discussions, arguing about implementation and integration interfaces, flame wars between "camps" - which contribute to constant lagging behind the Redmond giant, sometimes shotty code or a feature's death.
OpenOffice/StarOffice is great...but there's no integration with other apps like Evolution, Mr Project, GNUCash, etc. other than the export-to-suboptimal-format + import-and-clean-up method. All of these programs have well-defined APIs and interfaces, but no one's connected them, yet. Imagine, using Mr. Project to coordinate 3 developers, a project manager and a sales engineer, updating everyone's schedule in Evolution and tracking expenses in GNUCash.
When there's that level of integration, then GNU/Linux will grow to be as ubiquitous as Microsoft.