I have a DNS-323 with FW 1.05 and recently purchased a DNS-321 for additional storage after reading of the FW 1.01 improvements.
The issues:
1) I installed two WD10000CSRTL (1TB) drives before upgrading to FW 1.01. Formatting as two single drives got me the 94% problem that did not clear after 8 hours. I upgraded to FW 1.01 and reformatted only to get the same 94% problem. The only way I was successfully able to format the drives was to format with only a single drive in the DNS-321. When that one was complete, I shut down the DNS-321, removed the first drive, inserted the second drive and formatted it, then shut down, added the first drive back in and powered up. Both drives worked.
This is no different than the issue I had with the DNS-323 FW 1.05 with the same drive types.
2) The DNS-321 fan noise with FW 1.01 is louder than my DNS-323 with FW 1.05 running in the same cold condition. The fans have never shut off on the DNS-321 even though the drives are not running and the room is very cold (65F). The AV and iTunes servers and LLTD are disabled.