If this is your first server-side language, it's as good as any. The thing to do is focus on one, and after you feel you've mastered it, explore others and deduce your own conclusions.
I work with RoR and ASP.NET on a daily basis, but strangely enough, I prefer the ASP.NET world, but that has more to do with personal philosophy than it has to do with the language or the architecture itself. (I'm a bit of a control freak and I personally gravitate to strongly typed languages).
Regardless, I say give it a go. RoR is a great environment to work in, but before you jump right into Rails, get comfortable with Ruby as a language. Beyond web stuff, Ruby is a pretty cool scripting language if you land up having to manage a *nix box and can save you a boatload of time.