I cannot say exactly how big the patch is, because apparently the % meter accounts for the number of files needed to download and not the complete size. I believe there were around 70,000 files to download, but some are bigger than others, which means for example that 4%-20% could take ages but then it could zip up to 90% fast.
So far I have been patching for hours (since I've posted here about it) and it's downloaded 830MB, 17%, a little over 51,000 files remaining.
Here's a screenshot for clarity:
https://dl.dropbox.com/u/68463828/yallaupdate.PNG