I don't much care for Simon Willison's (or in this case, the person he's linking to's) implication that Java programmers are misguided fools in need of help (as opposed to engineers trying to earn a living by using the best tool for the job on hand, rather than getting all evangelical about their language of choice).

However, the quote he posted recently makes a good point - using immutability and other functional ideas does make for better-written and less error-prone Java. And many of us have moved in that direction already, mostly without any prompting (although since Haskell was the first language they taught me at Oxford, that doubtless influences my world view).