Welcome to the internet!
If no one complained about something as widely used and supported, then I would be very concerned. It's like windows: some people hate it and call out all its flaws while often failing acknowledge the flaws of their preferred OS. Some people wouldn't work with something else, but they'll still complain about using it. If we waited around for the perfect programming language, we'd still be using an abacus.
There are projects for which it is not the best option. There are projects for which it is a terrible option. But it is often a very good option for quite a wide variety of projects. So, under the principle that it is far better to know a few tools very well than a lot of tools very shallowly, it is a good choice.
Performance is terrible? AFAIK, Apache Cassandra is built entirely on java and that's good enough for Facebook, Digg, Twitter, and so on. I've generally had bad luck with performance on desktop apps in Java (and I think that's changed), but for other purposes, it seems rather ok.
And no, I'm not just a Java fan boy. What's paid my bills for the last 7 or so years is almost entirely .Net.