I am a Java developer in my day to day work but I'll give a few reasons: 1. The memory footprint of the JVM is significantly larger for a similar app vs. PHP.

I am a Java developer in my day to day work but I'll give a few reasons: 1. The memory footprint of the JVM is significantly larger for a similar app vs. PHP. Also, it requires a lot of tricky JVM option tweaking to get it to work in anything less than about 512mb. 2. The build environment is really heavy weight and complicated. Maven seemed crazy at first though working with it for a while finally got me used to it. It's still crazy complicated compared to rails/python. 3. Lack of code reloading when you hit refresh. JavaRebel fixes this, for a price. 4. Java code is really verbose. You have to become an expert at a lot of IDE features before you can get decent productivity. You absolutely cannot use a simple text editor or anything less than one of the big 3 IDEs (Eclipse, Net Beans, Intellij) and get anywhere. The future is bright though for the JVM. I have started to work more with Scala/Lift lately and I am really blown away at how fast and powerful it is compared to traditional Java development.