I just got back from the week long Zope3 coding sprintathon in Rotterdam. Lots of fun, very educational, and now I have even more obligations of code I need to write for free software projects :)
The sprint was an impressive commentary on the success of free software as a commercial enterprise, with around 25-30 developers from 15 different organizations. Unlike Zope2, which was in general developed by a single company - Zope Corporation - Zope3 is being developed in a series of coding sprints in addition to the individual ongoing contribution of developers. The sprints and development are done, in general, by programmers at companies whose business is based on Zope2.
There are 95 companies listed as Zope Solution Proviers on zope.org, but in practice there are probably many more, as well as even more companies who sites run on Zope. No doubt almost all of them are interested in Zope3, and quite a few are putting in some resources (e.g. giving workers leave for a few days to go to a sprint) to make it happen.
On the technical side, it's interesting to compare Twisted to Zope3. While they have different purposes - Twisted is a general purpose networking framework and libraries, Zope3 is a web application server, they are both fairly large Python frameworks.
Someone called the Twisted developers "abstraction astronauts", but compared to Zope3 Twisted is so concrete you could build bomb shelters with it. This has a price of course, Zope3 is quite slow and only does 1 request a second on my laptop, but it has not been optimized at all. Knowing the people involved I don't doubt their claims that they have clear paths for optimization, and I'm sure the final release will have decent speed.
In any case, the abstraction is a good thing. Zope3 is an inherently complex application, and the new design is quite superior to the kludge known as Zope2. And Zope2 is the best content-management oriented web framework I know of (the next person to point to their favorite PHP project gets a $10 voucher for Toys R Us where they can buy some more toys.)
Twisted has been running applications for most of its existence. For example, http://twistedmatrix.com has been running using Twisted's web server for about 2 years. Since this also includes user homepages and the #python wiki (MoinMoin CGI), this provides some real world testing under real conditions. In addition, a number of commercial and open source projects are using Twisted, some of which have already been deployed. Zope3 on the other hand has not been used for any real world usage, other than developing itself - not even a test server for the development project. This will soon be changing as a couple of projects will probably start using it once the alpha is out.
I am confident in the Zope3 source code quality however, beyond the design itself. The use of interfaces means there's a clean separation between the requirements and the implementation, which does of course suck in some places. In addition, there are a *lot* of tests. Twisted has 75,000 lines of code, Zope3 has 150,000. Twisted has 350 automated tests and about 15 tests that need to be checked by users. Zope3 has 2700 automated tests! This will mean refactoring to deal with real world requirements will be much easier.
All in all, I'm really looking forward to Zope3. I'd probably be jumping up and down going "GIMME GIMME GIMME I WANT IT NOW" except I'm trying to get out of doing content management website jobs.