Good & bad
Good point is the appearance of tape-raid, but surely they are not the first to do this? After all it is a simple adaptation of disk raid but with (presumably) some optimisation or HDD cache to get round the tedious linear access of tape.
Bad point is WTF do they quote 3:1 compressed sizes for? Who actually sees that in practice?
I suspect that if you are similar to FB most of your data volume will be compressed images (maybe compressed PDF docs in business environment) so you won't see anything like 3:1 compression. Maybe if you have a lot of sparse VM you might, but really that is a con.