So far I haven't had a problem, though I did wait until the official notice to update. The Main reason to update was that the recent updates of some packages required v6.2.2, and then there are some security fixes that weren't obvious if I needed them or not.
I was remaining on Moments v1.3.0 due to an upload from iOS bug. But the official temporary fix (posted on the 'community') did work: for affected user accounts you need to add an explicit access permission on the user's home folder to give that user full control, and then propagate to sub-folders and files. This mimics a rule that is implicitly already there (greyed out). And I suspect it is bug in how Moments package checks authorisation.
I had a similar thing with Download Station when setting up podcast downloads. Within DS, it would not let my admin user to create a folder in the destination location, but File Station would. I added the same type of rule to the destination shared folder and now Download Station works.
Anyway, for my use of DSM, I haven't run into any issues with v6.2.2 on either of the two NAS.