I have a little project with CanJS and Node on a Rest webservice. I found that the most important thing worth sharing for Models is some configuration for validations. But that also depends on the database you are using, maybe node-validator might be worth a look.
Personally, I found now, that finally the importance of good server/client separation (as JMVC encouraged for a long time) has become more accepted it is important to try not to mix client and server concerns up too much again just because both sides speak the same language.
I haven't used Geddy yet. But most server side NodeJS frameworks are more complementary to the client side MVC ones like CanJS. I found node-restify a good fit. Express for my taste is way too concerned with rendering views and handling sessions.
I guess that part that is confusing me a bit is that most of these node.js frameworks such as Geddy and TowerJS provide mechanisms for creating models, controllers and templating support just as the client-side frameworks do. Would using one of these frameworks make using a client-side framework unnecessary?
Exactly. That's why I was looking at Restify. Occasionally I am still working on my own little framework on top of that which hopefully will make creating REST services even easier and more HTTP compliant.