i'm not sure that's true, at all. can anyone verify this with real data, not just a reasonable guess? I think that it has little/no effect on load-up time, because the actual "Library" file that it loads is tiny.
I don't know, sometimes when starting up it shows a window with a progress bar for 3-4 secs where it is "loading iTunes library".
It has gotten worse over time so I suspect the size of the library does play a role in this. (I have over 10,000 items at about 80GB)