In what way do you feel like rails support for postgresql is an afterthought?

I've noticed some books / documentation assume mysql, but that's usually limited to the "and now setup your database" section.

I've been using rails + postgresql for a long time now (almost 2 years in production) and I can't think of a single problem that was due to not using mysql. Of course, I don't use every plugin or feature, so there may be something out there...