I installed the DSM 7 beta (it felt safe as I stil had my old WD Mycloud as main device). I will wait to move to the 220+ until DSM7 final is out. One other question though. Do you think it is likely that Synology will have an update path from the beta to final? Or would I need to start over once DSM7 final is released? Just to know how much effort I should put in on the DSM until the final is released.
With DSM6 when it was BETA, there was no need to start anything from scratch. It automatically switched to a full version from beta.
Since they say, you can not revert back to the previous version with DSM7, I assume that the switchover will happen seamlessly.
I hope this helps.