The common subset is most of the language, if you target 2.7 and 3.3. But yes, it has clearly caused extra work. But all the tools I use support Python 3, and I

The common subset is most of the language, if you target 2.7 and 3.3. But yes, it has clearly caused extra work. But all the tools I use support Python 3, and I'm looking forward to when new users routinely go for 3.