I've been using the 20% weekend code; it works fine. I just saw the note for the 25% off. Oh well. I do find I am buying the lion's share of my books from Kobo, not Amazon. Prices are generally similar but the discount code almost always leave things in favour of Kobo, even after tax. Amazon has a considerably larger selection of books I am looking for, and I really like the wifi management of my library with Kindle.
On balance, happy with both ... and I hope Kobo continues to offer % discounts as these just seem cleaner to me when browsing.