The class-based approach gave very little practical reuse, and it was not granular enough to allow us to easily add validation rules or customize the fields to return from a model. Lots of ugly code where you had to concern yourself with response codes.. I mean whats the point with a framework if you have to concern yourself with response codes? Isn't it the frameworks role to abstract away these details?
Most of my beef with the framework has to do with the design. It has abstraction in all the wrong places ... Inversion of Control (IoC) just seem like a complete afterthought in the entire design.
Now with Tastypie, I will admit it has a steep learning curve, and a conceptual overhead, but it does a much better job of abstracting away the internals and you end up with a much more correct and consistent REST implementation. In addition, it is better architected which makes it easier to extract base classes and override behavior, which is valuable if you need it to work really well with non DB models.
I will say that deep down I'm not really happy with either alternatives though. Tastypie requires too much code to get up and running and it takes too much time to get confident with it. Will def. take a look at the other frameworks mentioned in this discussion.