the key to "release early, release often" is that your releases are evolutionary. with GNOME that would be _adding_ Shell as an option in addition to the 2.x way of doing things and then later flipping the default.
this doesn't go well with people who thing that a new release should include revolutionary things or it's a 'worthless' release.
it is actually harder to do major changes with evolutionary releases, but the result is usually better.
We see the exact same issue in patches. It's easier to do one 'big bang' patch that changes everything and rips out an old system to put in your new wiz=bang solution.
but if you can go back and create a patch series that is evolutionary instead, it's much easier to get review and feedback.
In some cases you find that the users really didn't want the wiz-bang feature the way you initially envisioned it, but the evolution allows them to benifit from your work even if the end result ends up a bit different.
In other cases the mere act of going back and breaking the change down into logical steps ends up showing the developer places that things can be cleaned up, simplified, generalized, or otherwise improved that were not obvious in the 'big bang' change.