The only negative I've seen is minor: when I click on a bookmark in Tear Bookmarks in the desktop Task Navigator, it opens in a new window rather than replacing the webpage in the already-open window (like it did in the built-in MicroB Bookmarks).
i think you would find that for each that loved the microb behavior, there is one that hates it.
the only real solution i see if for the system to ask each time a bookmark is accessed from said menu, while a window is already open, if it should be opened in a new or existing window.