Although you can have many views in a library (don't know the exact limit yet but I have 82 so far), it seems that the library/list 'edit shared webpart' view selector dropdown only displays 47 custom views plus the 4 defaults.
I guess I'm going to have to try to find a way to change that limit….
Oh, and the list of views available in the dropdown aren't sorted alphabetically.
There's also an annoying bug that when editing the current view and clicking ok, you are thrown back to the published page and the settings for the toolbar have defaulted to 'full toolbar' even if you have previously specified summary or no toolbar. <sigh>
agoodwin