The article What is Ruby on Rails from onlamp.com helps explain all the fuss.

An excerpt:

You can usually divide web application frameworks and the developers who use them into two distinct categories. At one end of the spectrum, you have the heavy-duty frameworks for the “serious” developers, and at the other end you have the lightweight, easy-to-use frameworks for the “toy” developers. Each of these groups generally regards the other with disdain.

One of the most interesting things is that Rails is attracting developers from both camps. The high-end developers are tired of the repetitive, low-productivity routine that they have been forced to endure, while the low-end developers are tired of battling a mess of unmanageable code when their web apps move beyond the simple. Both of these disparate groups find that Rails provides sustainable relief for their pain. I don’t know about you, but I find this quite remarkable!