I generally run all my projects that use castle off the trunk. However it has been several months since I've taken any updates, mostly due to lack of time on my part.
As I'm upgrading there are many many changes which require me to update my code. Most due to the introduction of IController and changes from IRailsEngineContext.
One such instance is IResponse.BinaryWrite which seems to no longer be available.
As I dig through svn to try to find if there is a replacement method or why it was removed etc I am hit right in the face with how poorly svn handles branching and merging. The only log message in the trunk is that all these changes were merged back in in one giant commit. If you want to go see what those changes were you need to go look through the branch that was merged, but even then there's no way of knowing exactly which changes were pulled ( I just assume all.)
With git I would be able to see these sort of things and save myself a lot of time.