SVN 1.5 is installed on all of our newer servers. If you’d like to be moved to one of these servers, email support and we’ll get to it.
Wow, I totally fail. We do not currently have SVN 1.5 installed (I was looking at my private testing machine, which is running a rather experimental configuration), but we do have an issue open for our developers to build and install packages for either 1.5 or 1.6. I’ll keep you all posted on any developments.