They are relatively new to the consumer world, but old to say data backup operators at large companies. Actually, I haven't seen many DVD-RAM drive on the market at all! And if I do, they are probably £$£$£$£$£$£$£$£$£$£.
But yeah, they act like a floppy disk or zip disk, but with tonnes more space and very responsible read/write speeds. I hope to see them drop in price and out in the shops soon