SKY's4ME, easyjet haven't had great loads either at BFS recently.
Be careful what you read in the Irish press, they are not always supportive of their national carrier especially since the Shannon-Heathrow fiasco!
Aer Lingus is very confident about Belfast and so is British Airways. Aer Lingus are already seeing a strong performance on BFS-LHR and the other routes which are in direct competition with easy have seen much stronger bookings from around Easter onwards.
The only route I would be worried about is AMS but if and when EI get the KLM code share up an running I think even that route should see a huge improvement.