First one I've made it to, and there's definitely an interesting bunch there. Shame it had to be hosted at the Microsoft Island when OpenSim failed to handle 20 concurrent login requests...
A small security issue was raised at the meeting, and I used that afterward as a 'get-to-know-the-code' excuse. Had a hunt around the OpenSim code and found it pretty straight forward to navigate.
Having said that, the source is broken down into over 60 different projects / dll's. Now that suits me fine, but experience tells me some other people won't like that.
From my quick wonder around, my first impressions were, that there really is a lot there. There are chunks of stuff missing but, for the bits I noticed, there are placeholders ready to take an implementation when it's done. This bodes well. It gives me the impression that whoever architected the code had an appreciation of the entire requirements and was pragmatic about what they implemented and what they left until later.
I'm looking forward to getting into this more - but that all hinges on me off-loading more of the work I'm already doing. Which reminds me, I must finish of my Project Requirements and upload it to RentACoder.com :)