Finally made the plunge for this today, as the sale is still going (and I didn't want to risk it being over after Sunday).
In retrospect, maybe it wasn't that bright an idea to try and checkout all 79 of the ones I settled on at once, since Kobo seemed to choke in the middle of processing and then gave me an error message and told me to check my payment method.
On the other hand, it does look like all the books are slowly trickling into my library.
We'll see if some sort of receipt shows up tomorrow, or they get removed and I have to do it again, or whatever.
ETA: Oh, yay, I do have an official receipt now. Okay, now to hope that my cashback rebate for this via GCR goes through.