Well, it really depends on the application type. We are a Java and Ruby on Rails software house (http://codedose.com http://codedose.com), we also have experien

Well, it really depends on the application type. We are a Java and Ruby on Rails software house (http://codedose.com http://codedose.com), we also have experience working for investment banks, and for some cases Java with Spring or Play is the best way to go, especially if you think about apps with complex back-end. We have recently released an online market for physical gold trading capable of handling 10k+ concurrent users with horizontally scalable architecture and complex trading engine/accounting logic, and it's all Java. It has to be fast and there is not enough static or almost-static content to make caching effective.