Maybe I misread the point of Ian's post, but the biggest reason I don't lean more towards Zope is that the model isn't for me. While if I were writing my own ideal web system I would probably do so in Python (because I like the language), when I'm looking for something pre-existing the language is much less important. As Ian said, people choose Rails because they like how the model helps them work and Ruby comes from that choice, and people choose Zope for similar reasons and Python comes as part of that choice. If the python community wants to have a dynamite web development platform that draws in excited new people, then make one or refine an existing one, but perhaps the key to drawing developers is that it is a "dynamite web development platform", not whether it is in Python or not.
That said, I do need to look at Zope3 and reconsider whether it provides a model I'd be comfortable working in, and whether it would make my life as a developer that much better. It's been a few years now, I should probably re-codify the things I'm looking for and figure out what system will get me closest and let me easily engineer the additional things I want.