This free card is working and it is significantly cheaper than here in the O2 shop. Annoying for me was that I have waited in vain for nearly a week on the confirmation for activation. Then I looked around on the website of O2.
In my opinion, should be here in the product description is important to mention that you have to take care of the registration and has only 14 days. (Forms at [...] download. For more information in the FAQ on the website, section " Help ".)