I just opened a 1.5M XML document in TM. My XML syntax isn't all that lean, and it takes a while for TM to highlight everything and become responsive. Currently, I do not know of any way to open a file without syntax highlighting. That'd be one nice thing to have... The other would be for TM to pop up a little dialog if highlighting hasn't completed after, say, 10 seconds and give the option to abort the open, continue highlighting (until done), or open without highlighting.