Anybody know? I heard they did something like this for the Enhanced Edition (which I already got), but what could it possibly be now? 
That's pretty f'n insane for a patch.

Mine just showed that but then only downloaded a tiny bit and said it was done. Is yours redownloading the entire thing?

I dunno. I noticed it earlier, but it had already finished the download.

mine has been doing that for the last few days. usually only downloads like 168kb before it finishes. no clue what's going on with it.

Mine only downloaded a 2.3mb patch while I was in the shower. I'm glad I didn't see 16gb otherwise I'd shit myself with fear as I have an 80gb monthly cap and I already used 15gb redownloading the witcher 2 GoG version after a kerfuffle with steam cloud losing all my saves and not letting me use the saves I have stored on my harddrive.

Ok, after a while it jumped to 15 something GB and only downloaded maybe 200MB overall. Phew...false alarm.

Steam seems to do that a lot. It kept doing that for Company of Heroes as well.