I like Kohana much more than CI, if only for tossing PHP4 support.
However, but I've found that there is lots of fragmenting in the community/documentation. See the differences between 2.3.4 -> 2.4 (lots of breaking changes) -> 3.0 (almost entirely different framework). Which is kind of a bummer when using it for long-life projects (we have a few projects are stuck on 2.3.4).
That said - Symfony 2.0 looks fantastic, and very much like the next "Rails-like" PHP framework.
Exactly the same story here. Our primary product is stuck on Kohana 2.3.4 because of the lack of care that the Kohana team put into backwards compatibility. I wouldn't be surprised if they decide to essentially rewrite things again in the future either. If I could go back in time, I'd pick something else.
Kohana 2 was "just a php5 fork of CI", while Kohana 3 is practically a whole new framework. The "problem" is that Kohana team doesn't like handicaping new versions for sake of complete backward compatibility.
They just make the framework better with every new version, although in case of Ko3 minor versions are backward compatible (for example 3.0.8 with 3.0.1., but 3.1.0 will not be, at least concerning the response object and the ORM logics).