It's the media cost that will be the problem. It's just going to make ZERO economic sense to go Blu-ray recorder plus media when a solid burner plus single layer media is going to cost a fraction of the former's total cost (not to mention since most people already have DVD burners that are interested in Blu-Ray in reality there is no burner cost for the single layer media option, only blank DVD+Rs for pennies a piece)
For example, given your 600GB. Assuming you're getting good media for about 50 cents/pice. For 600 GB, you'd need about 140 discs, let's say 150 as you won't be filling every disc to the brim. You're looking at a total cost of $75. End of story. For blu-ray you're looking at, best case scenario, $250 for the burner, plus a minimum of $1 per GB for blu-ray media (in the best case scenario but will likely be more due to costs of manufacture) so you're looking at another $600 assuming you're filling every disc to the brim (which won't happen).
So best case scenario for your backup is:
$75 for DVD+R
$850+ for Blu-ray
Gee, I wonder what makes more sense (and NO, no time saving in the world is going to justify $775+ of wasted money) Blu-ray recording=DOA