Neat news from InfoQ. I got to visit Gemstone when I was in Portland for OSCON. Long story short, if you want object databases for your Rails apps, it'll be easy very soon. This is vitally necessary for complex problem spaces such as international shipping and warehousing.
It may also represent a much better model for Web application persistence in general. I've blogged about this, Evan Weaver spoke about it at RailsConf 07, and DHH once commented also that he doesn't like databases and essentially uses them as hashes. It's entirely possible that the OODB model could be much better.