I can see the vast improvement in the code over manually writing AST.  But we can't have a snapshot dependency in Play - snapshot dependencies can change or even disappear at any time, if that happened, it would effectively shutdown all development on Play until it was fixed.

Now if we do get a proper release of macro paradise, then this implies that we are making a commitment to upgrade to 2.11 in Play 2.3 and drop support for 2.10.  The reason why this is the case is that I'm pretty sure that the Scala team makes no effort to ensure backwards compatibility of the compiler plugin API between minor releases.  So, macro-paradise may work with Scala 2.10.3, but there's every chance that it could break against Scala 2.10.4.  This will mean users of Play 2.3 on Scala 2.10 could be locked to a particular Scala 2.10.x version, breaking the requirement that Play be forwards compatible with supported Scala minor releases (and this is a requirement that, when broken before, has got us into a lot of trouble with customers).

So, I'm not sure whether we want to cross build Play 2.3 against Scala 2.10 and 2.11, but I certainly don't want to exclude that possibility now.  I'll need to check with Typesafe as to what our plans are here.