I am not sure if this conflicts with your suggestion or not, but I greatly prefer when the overall window stays the same size when opening the file browser and not push the overall size out and to the right, as TextMate currently functions. BBEdit does it the other way, when you have your windows set up as you like them and open the file browser it messes up my layout. To me it makes more sense to consider the overall window one unit, not a separate window with a file browser adjacent to the editor window. Perhaps my preference doesn't conflict with yours after all, you would just have to close the file browser first before hitting new file I guess, but I think they do, you are pretty much saying the file browser and the editor should be separate. I prefer them as one.