My client has a computing environment that includes six F630's, an F540, and an F330, all doing CIFS, NFS, and quotas. In January, we decided to get them all running the same OS revision, and based on the bug list we chose 5.2.1 as a target.
If you are thinking of moving to 5.2.1, I encourage you to think carefully.
I will second that. We upgraded our 630 to 5.2.1 on Friday, and it hung this morning. Color me not thrilled. That said, I wouldn't expect Netapp to have magically broken the "sawtooth bug curve" somehow, so I guess we should have simply waited for 5.2.1something.
Paul