I had no problem getting the free wi-fi to work on the flights to/from MIA I took back in October. As part of the free package you get full access to WhatsApp and FB Messenger, although sending images seemed to be problematic. Also If memory serves, new notifications were delivered to my iPhone's lock screen from other apps, such as Gmail, Yahoo Mail, FB, etc, although I was not able to access the full content in the relevant apps. So it's not that bad.

Amusingly I was in PE on the flight back from MIA, so I had to log in with my IB+ account in order to take advantage of the free messaging service (it's not necessary in the J cabin, as your last name and seat number are enough to access the service), and I couldn't remember my IB+ password. SInce access to iberia.com is always free on the on-board wi-fi, I was able to set up a new IB+ account on the spot and used the new credentials to access the free wi-fi service.