I'm leaving a PHP job soon to start a Ruby job. The language was not the decisive factor, but it was a factor - I wanted to move to Ruby at some point.
The company I'm leaving solves complex, interesting problems in solid PHP code. There are developers here who are a lot smarter than I am. So my attitude is far from "you guys suck" or "I'm better than you."
But when I look out over the programming landscape, I see a lot more energy and activity right now in the Ruby community. A lot more people building new things and inventing new best practices. This is a simplification, but it seems like great ideas come from Rails and move back to PHP eventually.
PHP jobs run the gamut from high-tech and awesome to grunt work. Rails jobs tend to be more cutting-edge, because the technology is newer and there's just more stuff happening there.
So for me, the question is this: if the Ruby / Rails community is the leading edge for new ideas, and the AVERAGE (not to say all) developer in that community is better, and the AVERAGE job in that language / framework is cooler, doesn't it make sense for me to move that way? All other things being equal, isn't that a good career move?
It isn't snobbery, it seems like the most pragmatic thing to do. This is on top of the fact that I genuinely like the Ruby language a lot more than PHP.
So I don't think you have to feel slighted personally. And I'd expect this cycle to repeat someday: there will be a lot of Ruby / Rails apps that need maintaining, and a lot of developers will prefer some hotter, newer thing. Just the way it goes. But it's nothing personal.