I would so love to use Java as a server-side tool - if only it had the widespread availability and low-cost of PHP. I do Java in my full-time job, and my own stuff is either PHP or Perl - because of its availability on standard web hosting accounts.
Java is too pricey for normal use, and that's why its always going to be an enterprise level infrastructure. Pity.
I've seen a lot of people (mainly developers who blog) migrate from PHP to Python over the last year or so. It makes sense - Python offers most of the benefits of PHP whilst moving closer to the Java-approach. I'd be tempted to jump over to Python if it started appearing in typical web hosting packages.
Unfortunately, however good Java is on the server, it takes running your own server to be able to use it to its potential. And that's too expensive in comparison to PHP.