Activated my AT&T 1520 yesterday with a backup from my 1020 running Dev Prev. My SPro didn't like that and couldn't connect to the 1520 so I did a reset, not including the Nokia Software reset (so it still has Dev Prev onboard).
Upon reset, I immediately installed and activated the Developer's Preview. The phone was updating apps and asked to be re-started. I did that and it is now running Denim.
Upon reset, I immediately installed and activated the Developer's Preview. The phone was updating apps and asked to be re-started. I did that and it is now running Denim.