First, a wrap-up of the last Quiztime. For an excellent explanation of the issue, read this comment. Also note that this is not the most nice way to do plugins with C++, it’s a boiled down piece of code I debugged.
I’m not sure if there is some confusion about the current development model of Shotwell. I noticed that some distributions seem to try to pick up the current development branch (0.25.x). I strongly advise against that at this point in time. It has just seen a major change in the Menu handling code and might still have severe usability regressions.
While I appreciate any testing of the code, I would really not have the current unstable version of Shotwell stuck in a released distribution. If you want to try those releases on Ubuntu, there is an unstable PPA available.
So to sum up: Shotwell follows the “traditional” version scheme of “Odd is unstable, even is stable” and roughly tries to stick to the GNOME release schedule.