Whenever I talk to developers in the Java community about Rails, the first question out of their mouth is usually "But can it scale?" Today, David has written a nice post titled It's boring to scale with Ruby on Rails.
The one thing that I see time and time again is that Java developers don't seem to realize that some of the highest traffic sites on the net are using LAMP stacks similar to what Rails advocates. IMHO, I don't think "Rails can't scale" is a valid argument. In fact, I don't know if there's any argument or way to put down Rails anymore.
As a developer, my guess is the rates for programming in Ruby developer are less than for programming in Java (unless you're a Ruby Superstar of course), so that's one reason not to program in it. However, since Rails is one of those new bright and shiny things, chances are you might be able to get high rates for it. As far as Enterprise Adoption of Rails, unfortunately I think that's still pretty far on the horizon. I think the hardest part is convincing management that they'll be able to find developers to support it. Mind you, I didn't say good developers, just developers. Period. This is information I've gathered from talking to my Java developer friends.
Try convincing a Fortune 500 company to program in Rails vs. Struts and they'll probably choose Struts because there are thousands of Struts Developers. Is this a good decision on their part? I don't think so. I think it's more important to hire smart people that can learn a technology, rather than hiring those that know a technology. Of course, if someone knows a technology really well, there's probably no harm in hiring them.
I think Rails can become a real contender in the Enterprise if managers can be convinced that it'll be easy to maintain Rails application. Remember that most of software cost is maintenance. Because of this, the whole "it's super productive to develop with" doesn't matter so much - does it? Are Rails applications easy to maintain? My guess is yes, but how do you convince CTOs and CIOs? Another thing I think Rails needs for Enterprise Adoption is good tool support. Drag and Drop type of stuff. Why? Because management loves that stuff (because then they can develop apps) and it's a great sales tool. ASP.NET has been successful because of Visual Studio, not because of its ease-of-use and simple syntax.
Will I learn Rails and use it to develop applications? I certainly hope to, but it's hard enough convincing companies to use something other than Struts - so I don't know if I'll have much luck in selling Rails. The one cool thing about my new job at Virtuas is its an open source company, not just a Java open source company. This opens the doors for me to learn about Rails (and others) and compare them to Java Web Frameworks.
Update: Aaron Rustad has written an interesting article for DeveloperWorks that compares Rails to Struts+Hibernate: Ruby on Rails and J2EE: Is there room for both?