It appears there are differences in behavior between the 2.x stable versions of ext/memcache and 3.x devel versions, specifically in [3.0.3](http://pecl.php.net/package-info.php?package=memcache&version=3.0.3):

> Scalar data types (int, bool, double) are preserved by get/set

I'm going to run some more tests using different versions to iron this out. 

If I can confirm the version that changes this behavior, we might be able to return a different compatibility spec based on the installed version (is my current thought). Details to come...