But everyone except Play! and a few others seems to be jumping the new syntax bandwagon.
Being a php/python/Java developer I'm afraid I'd trade all improvements after generics for a no restart required jvm
It lets you do arbitrary hotswapping of code, rather than only swapping method bodies. Not appropriate for production at this point, but you can install it on top of any Java 6 version prior to update 26 (not sure about Java 7); it's pretty useful for doing rapid iterations during development of large-scale server apps or swing applications.
Also it supports picking up changes in the configuration of major frameworks, like spring, for example.
Basically, with JRebel you can develop in java as you would do in python :)
disclaimer: I'm employed by the company that develops JRebel, but this fact doesn't make it any less awesome.
When working with Haskell and discussing why you would want to use let vs. where or if vs. guards, Bryan O'Sullivan explained it to me by borrowing a term from journalism: Don't bury the lead.
You want to put what the function does right at the top. The first thing it should tell you is that it prints hello for each person in a list. Then you can put the details of how that's done in definitions below. It allows you to write functions so that they are easy to read and so that the structure of the semantics are separate from the implementation details and the requirements of the system.
Java's rigid boilerplate has always stood in the way. It would be like if every newspaper article had to list all of its sources, with full names and titles at the start of an article and then had to list events in chronological order. They would be mind-numbing to read. Sometimes I just want a good juicy sound byte right in the first sentence so I know why I should be interested.