well, it's one thing to take risks, it's completely different to write a production application in a language and framework you barely know. you end up spending a lot of time looking up things that you already knew how to do in the other languages you were familiar with. also, what happens if the application goes down for unknown reasons and you have to troubleshoot the application at 3am on Sunday? It's sometimes wise to stick to the things you have mastered and learn new technologies on non-critical applications.