It's surprising how hard forms seem to be to get right. Forms in Pylons were terrible too... I've not used other declarative form systems besides this but it seems like a terrible idea in general.<p>Do anything even slightly complicated (say validations dependent on other field values) and you end up having to extend the framework in truely monstrous ways just to get it to happen. (On a side note, using the validate decorator in Pylons is NEVER the great idea it initially seems to be).<p>In the end I replaced the form system with my own that let me work procedurally instead of declaratively (without the need to memorise the multi-tiered internal form handling API) but I could still plug into the existing declarative system (no need to re-invent the wheel).<p>In that regard Rails form handling is a pleasure to work with. Validation is just as easy for simple and complex scenarios. Integration with the ORM is fantastic removing a tonne of manual pain when constructing forms.