Yeah, the notion of bitching about Disney changing sacrosanct plots is pretty ludicrous at this point. Either you have accepted that this is what Disney does or you haven't and you don't watch Disney movies ever. In the case of Rapunzel, where the plot is about a page and a half long, I have to say that going off and being a pirate sounds pretty cool. Especially if she gets to keep the long hair while she's a pirate and does creative things with it.
And anyways... are we ignoring the prince rescuing her in the first place? Cause if we aren't, it's not like there isn't plenty of room to have the original Rapunzel story take place mostly verbatim in the first 15 minutes, and then have the movie be about what happens AFTERWARD.
Semi-unrelated news: A month ago I had been thinking it'd be neat to have a video game where you played as Rapunzel escaping from your tower using your increasingly long hair as a weapon/tool (there IS such a video game but it's a terrible flash one). I assume there will be a videogame tie-in to this movie ('cause there always is). It'll probably also be terrible, but still tickles me somewhat.
Edit: I wanted to amend that I AM disappointed that we aren't getting a movie done entirely in the style of the concept art. BTW, is there a link to any CGI stills?