Contrary to Paul Graham's misguided treatise on Great Hackers, this great hacker (by his definition, I prefer the term "developer") absolutely does use Java and loves it. You can pry it out of my cold, dead hands kind of love.
Side note: coming from an Objective-C background, I was initially very dismissive myself of Java. I still prefer many aspects of the Objective-C syntax, and Objective-C has killer runtime libraries ... but I've grown to love and be reliant upon Java type safety, and garbage collection. Both are pre-requisites for solving problems in an object oriented way: using large numbers of small, simple objects.
I feel there is a kind of insipid game out there I call "chase the gigahertz". Every time the language (COBOL, then C, then C++, then Java, now Ruby and friends) catches up to the available computing power and the available libraries are in a state where you can actually get something accomplished, there's a lemming-like urge to jump ship and start all over again in the latest and greatest ... with a less efficient, less optimized environment that pushes the performance barrier back up and out of reach.
Wait. Stop. Ask yourself "why?". As the differences between generations of languages become more and more subtle, you have to ask yourself ... what do I gain by switching? What cost do I pay? Am I throwing out the Baby with the Bathwater? Sure, you'll be incrementally more effective at doing the kind of things that look good in demos and tutorials ... but the moment you reach for your handy XML parser and it isn't there, or a friendly GUI toolkit and you have to start from scratch. Database access. Command line parsing. Transaction management. Yes, analogues exist for all of these, but you'll be starting from scratch to learn their APIS, quirks, bugs and workarounds. Just how compelling is that nifty bit of syntax, those couple of characters you don't have to type, that convenient built-in function?
For me, Java hits a terrific sweet spot. Vast numbers of open-source libraries. Very competent language. Minimal amounts of stupid syntax. Of course, there are things I'd change ... but in my analysis, its not about the language syntax its about how you use the language. I'm a framework guy; when I get annoyed at writing dumb, repetitive code I build a framework to take care of that dumb, repetitive stuff for me. I write it once, test it, forget how it works. Tapestry saves me a lot of trouble when dealing with the ugly intricacies of web applications. HiveMind saves me a lot of trouble when building complex apps from lots of simple little pieces. I don't throw out years of effort and hope some new language will solve my problems for me ... I face up to my issues and fix them right here, right now, in Java and be done with it.
Java is good enough. Sometimes "good enough" today is better than "ideal" tomorrow. I can get insanely great things done in Java today, and tomorrow, and the day after.
I'm not saying you should be complacent. Dave Thomas recommends learning a new language at least every year, to give you more experience, more insight into new ways of accomplishing things in your language of choice. I hope the Java language designers to the same, and give us some stuff we could use (such as continuations and closures). As a software craftsman, your technique should transcend any one programming language.
But back to Paul Graham; he's making that tired claim about productivity, as if productivity is linked to characters typed. So typing productivity trumps everything else? As you can see, I don't think so. I think he's fallen prey to a bad analogy ... that because some great hackers chose to use scripting languages such as Perl, Python and Ruby then all productive developers should use those languages for all chores, great and small. He's decided that one language (or class of language) is universally correct, and he's using that as a litmus test for being a great hacker.
Whereas, I think "the appropriate tool for the job", scripting languages for simple, scripting things. Power languages, such as Java, for long term, high quality, maintainable development. Individuals can move mountains, if they have the right tools. For the applications and frameworks I build, the right tools are Java, the Java runtime and the innumerable Java libraries.