I did some poking around and read that CM has changed their release model for CM 11. Where they used to label releases as "nightly" (bleeding edge features, testing), "Release Candidate", and "Stable", they now use only "Nightly" and "Milestone". I flashed CM11, Milestone 6 to my Nexus 5 last night, along with the GAPPS for KitKat. Different GAPPS kept crashing after the flash. Some more poking around and I found that this seems to be a recurring issue and potential solutions include wiping the Dalvik cache before flashing, and correcting issues related to multiple instances of devices having permissions on G+. I fixed my G+ issue (I hope) and will try again today. In any case make sure you have a Nandroid backup in case things go awry.