Quite the story, and it sounds like quite the attempt to get it to upgrade. I'm really surprised the NAS didn't just do the right thing.

I was curious, and found my ReadyNAS is running 2.6.17. I'll have to see if they bump that up from time to time in the updates. It handled the addition of a 4th drive without incident, so I'm comfortable in saying it should be ok if I start replacing drives with larger ones.

Had a bit of a scare recently with it as well, since it is running all 750GB Seagate drives. Firmware though isn't one of the versions affected by their bug, so thankfully I'm not expecting the drives to drop dead prematurely.