* I'm wary of Node.js because it's so young, I'm a touch worried about it crashing and it requires a new set of JS-derived drivers/libs. But it has a huge range of frameworks that run on it and huge community.
* RingoJS seems like a very solid foundation and it gives access to a huge range of Java libs (of ever-varying quality). But I'm not in love with its programming model and it has a relatively small number of add-on frameworks and a small community.
Any other contenders I'm missing? Better to stick with Django?