[rjhackin]

Java is a good language for web development. It's mature and most of the big companies use java. Java in terms of popularity might have slowed down but JVM as a platform will stay for a longer time. I use java for my day job, but I did learn php, python and ruby on the side just to build some small apps as part of learning. It's fun to learn additional languages and to know where each language shine.

I haven't worked on Play that much so I'll let others who have used talk about it. Spring framework is another really good one you can give a try.

The reasons why startups prefer anything other than java might be rapid prototyping, bleeding edge and probably hosting costs.