I just received the replacement drive from the RMA of the dying one, and they kindly sent me a 750GB drive instead of the same 500GB model. Thanks, Seagate!
Too bad it’ll be part of a RAID-1 array and limited by the smaller drive’s size… I can probably take the extra space and ‘join’ it to the scratch drive for even more MythTV recording space, though. I’ll just have to read up on all this fancy new LVM stuff…