how many people, honestly, paid any attention at all to the trunk builds before the next major release
How many people used the "stable" version while Emacs 23 was being prepared for release? I don't know of anyone; Emacs 23 had too many useful features for anyone to wait.
Notice how Emacs users had the option of using an "unstable" version before it was released, whereas Textmate users don't have that option.
Taking a long time between versions isn't the same as going completely dark between versions though, is it?
I mean, people could see what was going on in emacs as it was being developed if they were curious. And as far as I'm aware, there weren't significant rewrites between versions.
Delicious Library. Took Shipley over four years to ship version 2, and it was rewritten at least once, and possibly twice, before it ever saw the light of day.
I can't think of a time where it's worked, but I'm sure there's at least one example of it happening, right?