The company behind Maglev, Gemstone, is already in the business of doing OODBs using Smalltalk as the language, and they have some big clients. I don’t really know much about how it’s working out for them, though.

For our web service, I have a couple reasons for not choosing C#.

* PHP, Ruby, MySQL, all these things are free, and so are some nice development environments for them, whereas Windows, IIS, and Visual Studio Pro are not.
* When it comes to web servers, I have way more experience managing real Linux systems than I do managing Windows systems, and right now the overhead of a switch isn’t worth it.

I have tried Mono, but not much.

Are you working with any clients or partners that are using OO DBs in their production systems today? Aside from the design elegance that these systems offer, I’m curious about the performance implications of these solutions. In my industry (finance), a DB that outperforms relational DBs for pre-planned and designed-for searches during trading hours, and then slows down somewhat for the ad-hoc queries we have to run overnight to aggregate all the data from the day would be fine in theory. However, it’s the possibility of the constant design changes required during the life of a financial software system resulting in complexity going through the roof and performance being shot to hell that make switching from relational to OO DBs a scary proposition. That being said, I’ve read that companies like Ameritrade and Sungard have already tried this with certain systems. Not sure what their experiences with the technology have been like, though.

What’s the reason for not using C# on your current project? Is it just a platform dependency thing? If so, have you messed around with Mono at all?