We had Java services that produced JSON, some that used JSPs, and a variety of others. TDD works in some cases, but if you ever wanted to do manual testing - for example, actually see the UI you were working on with real data - that meant redeploying the server after every change.

Play makes this dramatically faster/easier. TDD is better with Play as well: the plugin support, strong test tools, and sbt's ~test command are amazingly productive.