Hi, this is minor and it might not even be worth fixing. It might be browser specific: I'm on Firefox 3.0.15.
If you click "Preview Changes" while editing a post, it'll open it in a new window.
That window is then designated as "the" window for all future previews.
If you switch to that window and then start editing in that window, and click "preview", then instead of launching a new preview window, it will load the preview in the window you're currently in-- since that is the designated preview window.
One other minor thing, the "Version" pulldown menu here at wordpress.org still doesn't have 2.8.5 as one of the options ;)