Productivity in Java vs. Rails
I am far more productive when writing Rails code than when writing Java. I just realized that one of the reasons for my lower productivity in Java is the need to recompile every time a make a change to a page on the site. In the 15 seconds or so it takes to recompile and redeploy to Tomcat, I get bored and am apt to go check my new favorite news site, popurls, or my RSS feeds, or (less likely) post to my blog. Suddenly those 15 seconds have become 5 minutes. And this happens many times throughout the day.
With Rails, I make a change, refresh my browser, and there it is. On to the next step.