I don't think there will be anything wrong with the servers on launch day but it doesn't hurt to download as a backup.
Same, just downloaded the update in about a minute now as a Plan B for Friday. I don't anticipate a problem with the update on PSN but better safe than weeping fury at 1230 AM Friday.
EDIT: just because it's there downloaded what appears to be the 859MB full install PUP as well, about 4 minutes. *Really* hope I don't need that file for anything any time soon lol.