I am a .NET Developer (in my job). I have tested RoR and I think it is fantastic. Programming makes fun and is very nice not to code so much code.
Very good AJAX integration. Unit, functional testing, integration testing integrated (and very easy/fast to use). I think the complete framework is focused on agile development.
Very productive framework - the best I have ever seen (until now). Caching, MVC ... integrated too.
An OR/Mapper is integrated too
And the programming language Ruby is very modern. It is much mode dynamic and not strongly typed like C#, Java,... it has mixins, ... and you can extend a foreign class without modify the source class.
I think the future in programming are not strongly typed languages - see F# of Microsoft research.
With scaffolding you can reduce the code you have to write or the drag and drop actions you need.
Deployment is managed with Switchtower, ... very cool.
I think RoR can have a big potential for the future. The community is very active and RoR 1.1 will be released soon. The people are very friendly and have nice podcasts and videos.
Since I know about RoR I have fun in programming again and I am much faster and more productive. I hope that RoR will have such a success like PHP. Java and .NET are in my point of view old technology (about 10 years) and have a syntax like C/C++ (much older).