Why do you use framework X?
bad_user: For me I based my choice on modularity, available components and available documentation.I got tired of working on dozens of authentication/registration systems, or admin interfaces with sortable tables ... that's boilerplate that distracts you from the purpose of your project.I'm currently using Catalyst (Perl) for heavy-weight projects. I like that I have CPAN modules at my disposal.I'm also playing with Django (python) ... I like that it has already built independent modules (see Pinax / django-cms) and a customizable admin interface. It also has very good (free) documentation. I always wanted to get familiar with a CMS platform like Drupal, but I haven't found any that I liked, and Django seems like a good alternative.I don't like Rails because currently it is too monolithic. There's no way you can replace ActiveRecord with little effort without losing functionality. It is also too heavy for my taste and makes too many assumptions about my application. Of the projects I worked on this year, none of them fits the Rails model.I took a look at Merb (Ruby) and it looks good. But it doesn't have a large following. Version 2.0 will be merged with Rails, so Rails 3.0 looks promising.I don't care about language choice as long as I like the language :)