I've been working on the microsoft stack for about 10 years. Started with classic asp, moved to asp.net webforms and eventually to asp.net MVC. My last few years of working was mostly with asp.net webforms but I launched a semi-successful website on asp.net MVC 1.0 a few years ago that I sold for a tiny bit of money (it wasn't big...the point is that it was a fully functional site that worked well enough to get purchased).
I recently found some freetime and was without work (by choice) so I decided to learn Ruby on Rails. It took me awhile to learn the whole *nix way of doing things, the command line, finding a good editor (vim :), learning the testing tools, learning BDD, etc. It was a STEEP learning curve for me personally but all along the way I have been loving it.
Now, I haven't looked for a rails job but at this point, just 7 months into it, I'm willing to drop my 10 years of experience on the Microsoft stack (and the salary that comes with it) to work fulltime in rails. For me, it's just THAT MUCH better than asp.net MVC. Now, I haven't used MVC 2 or even 3, but all I see is Microsoft trying to play catchup with rails. Take their new NuGet plugin system as an example, it is a straight up copy of the ruby plugin system. Take the dynamic feature of c# that's coming...isn't that a copy of ruby which is a dynamic language? I hear great things about their razor view engine but rails has had HAML for years (not sure if this is a good comparison as I'm not too familiar with razor. but notice it took MS until mvc 3 to introduce a competent view engine). I don't know if Microsoft is using something to compliment css like sass but if not they should.
I don't know, when I compare rails to mvc I can't help but feel like rails does everything better. Rails is easy to do TDD/BDD with, it uses git, the devs live in the *nix command line, their deployment methods are so simple, they are passionate about open source and giving back. Microsoft was so hard to do TDD/BDD last time I checked, people still used VSS or Subversion at best, deployment was usually FTP, there was so little community involvement compared to rails/ruby.
Anyway, I didn't mean for this to become a Microsoft bashing post but I guess my true feelings are coming out :) Anyway, the coolest thing about ruby/rails is the community. Take a look at the awesome open source projects in rails on github and you'll see what I mean. Go compare github.com and codeplex. Take a look at these things, please investigate it yourself, I mean really give it a chance like I did.
For me, it's really about how much enjoyment I've been getting out of rails/ruby. If you are someone who cares most about your craft as a programmer I say go for rails. If it's more of just a day job I say stick with Microsoft and asp.net MVC.
Sorry if I offend anyone, these are just my personal views.