In this article Paul Murphy tackles the problem from interesting angles. He doesn't talk much about Cocoon in detail, but what I found interesting is his view on how using software that does not require licences eases development.
Being able to develop an enterprise-class application on a standard system with no license costs before moving it to real production hardware can make or break many projects: no need to spend much money upfront before being able to experiment!
An I like his conclusion: Linux and Cocoon is it!