Still using gotogate and today had another issue :

This time, my flight got cancelled and I did get an email from them. Was offered an alternative flight 6 hours earlier on a different carrier which wasnt suitable and when I asked for a refund instead, was told that gotogate will apply a 10 pound per person charge as a same day alternative was offered.

That being said, ive also had many problem free bookings too, so I would still use them again if they were significantly cheaper than booking direct with an airline.