We ran into an issue regarding Strings in UDTs when upgrading to Spark 1.4.0-rc. I understand that it's a non-public APIs, so it's expected, but I just wanted to bring it up for awareness and so we can maybe change the release notes to mention them =)
Our UDT was serializing to a StringType, but now strings are represented internally as UTF8String, so we had to change our UDT to use UTF8String.apply() and UTF8String.toString() to convert back to String.
