symfonynerds has been running a survey. 250 symfony developers filled it out and the majority answered to question 8:

I have never developed in another web application framework

I consider this very alarming. If symfony is you first framework, then it should not be your last. Good developers need to know multiple frameworks, libraries, design patterns, concepts and so on. There is so much around that it would be very ignorant to stay with one player. You might be missing much better choices for other scenarios.

When reading the Whats new in Doctrine 2.0 slides I was very happy that Jonathan did look around. Doctrine 2.0 was redesigned to follow the Java Persistence API (and inspired by Hibernate).

This also brings up an interesting aspect of specifications: They are not only valid for the language they were designed for.