I just read a useful article comparing Ruby on Rails with some J2EE technologies. Aaron Rustad provides a clear and short comparison of the two architectures and winds up with some good advice.

I have been getting more into Ruby on Rails, but there are two things holding me back (a little): my huge investment in using Java server side technolgies and the clear tendency of my customers to want Java development. Still, Ruby on Rails is an excellent web application framework.