[nickv]

Fast Java code that is smartly written is really fast. There are lots of real world Java apps out there that you might not realize are Java --- I've read somewhere that Google Adwords is in Java, for instance.

The problem is, there are lots and lots (and lots) of bad Java developers out there --- it's the "safest language" there is (to learn if you want to make a buck or to hire devs if you want to play it safe as a manager at BigCorp), so you often see badly done outsourced work written in Java. Also, lots of Java code out there lives in non-Agile environments (so it runs on very outdated stacks.)

That being said, if you used a purely modern Java stack (probably some Guice, Wicket, Resin, JDK 7, etc) with super smart people you will be highly performant.

(Note: I haven't done pure real Java dev since the Struts days and Java 1.5, so the tech stack above is just me guessing at what the latest/greatest is.)