I don't know what's changed in 2010 but depending where you initiate opening a file it might open in the wrong docking area. For instance if I compile a project and get a list of errors and double click one of the listed errors the page will open up docked in the same region as the Error List window, wherever that may be at the moment, but ONLY if the file in question isn't already open in the IDE. My Error List window is docked to the bottom 200 pixels of the IDE so of course I don't want a file to open up down there, its useless. Same thing with the Find All Symbol Results window. If I double click on a result in that window and the file isn't already open in the IDE then the file will open in the same region as the Find All Symbol Results. There are numerous other examples, even occurs from the Solution Explorer depending on which docking area was last focused.
This is not how 2008 worked and not how I want 2010 to work either. I want all documents, regardless of which docked window I initiate the open from, to open in the main docking area.