In a customer project right now I need to be able to work and evolve code fast, with a relatively complex model. And by fast I mean that I want to cut away as much as possible of the efforts related to persistence. Generally this is what OODBs excel at.
In the Squeak world we have GemStone (commercial), GOODS and Magma as “full fledged” OODBs. Last century :) I worked with GemStone (both Gemstone/S and /J) and its a great product - but I want something lightweight and open source. And simple. And hackable. And new. :)
I also used Magma in the Gjallar project, and while I respect it highly - this time I want to try something with an “externally supported backend”. I also had a mixed performance experience, but this was “pre Cog” and Magma has also surely evolved lots since then, and I am not sure we did everything the way we should have either.
SandstoneDB could also be interesting to look more closely at, but since I have been working with Nicolas Petton on improving Phriak (Riak interface for Pharo) it was natural to take a look at one of his “under the radar” projects - Oak, an “OODBish” solution on top of Riak. At this point I have been doing much more than looking, in fact I am hacking on it! And oh, yeah, of course there are lots more persistence options available too.