I bought a small nRF51 module from a german vendor on eBay, and it arrived yesterday.
But I have not had time to even solder some tiny wires to it.
BTW. if you are playing with nRF52, I hear the first version of the device has a number of Errata in its silicon.
There are work-arounds for this, but its the reason why at the moment I only bought one nRF52, as I could not confirm the revision number ( as it is inside a metal enclosure on the PCB)
There is a bunch of errata (like with any other device). The only real bad one was SPIM sending an extra byte if the transfer is only 1 byte. Everything else seemed to have reasonable WARs.