OK, I didn't read enough fine print before I plunged in, but my version of the nrf51822 I have on a bunch of boards isn't supported by the new SDK.
In a premature onset of feng shui, I have lost the old one, and the website doesn't seem to want to give me the old one anymore.
Help? Where can I get 4.4.2 (I think that's what I was using)?