The anticipation of the SMART train system http://main.sonomamarintrain.org/, set to roll out in 2014, is drawing more people from Marin and SF to Sonoma by offering the 101 Corridor, between Cloverdale and Larkspur, a level of connectivity, not previously available.
Petaluma does not have a lot of retirement communities (aside from one on Petaluma Boulevard South and a number of Senior mobile home communities) I have helped a number of retiring people relocate here recently.
In terms of unique charm and value, Petaluma surpasses any town out there, in my opinion.
I hope this has helped to answer your question.
-Kim, Community Manager