Since a comparison with Ryanair has already been made, I'd like to speak up in favour of the latter.
I am a very frequent traveller on two routes on which the two airlines compete and prefer to travel with Ryanair if at all possible. This would be true even if all other factors such as schedules and fares were equally appealing.
There used to be four main reasons for this, although my more recent experience with easyJet might mean that I need to reconsider the first:
1. Punctuality.
2. The "boarding experience". I am always in group A and find it unpleasant to have to fight my way through those in group B who seem intent on blocking my way and making it as difficult and unpleasant for me to board as possible. (Andy, are you listening?) Being polite, I find myself repeatedly asking people "Are you in group A?" in two languages because it isn't clear if they have been called forward or are simply morons milling around and blocking others' access to the gate. Not only is the experience typically awful but the anticipation of it is stressful. Compare this with Ryanair's Priority/Non-Priority, especially at airports like Stansted with two orderly queues clearly signposted and with dividing tape.
3. I prefer Ryanair cabin crew.
4. Price. For my pattern of flying/purchasing decisions, easyJet is rarely as good value as Ryanair.
Now that easyJet has abandoned its "miles" credit card scheme, there's even less reason for me to use them.
On the other hand, I do realise that if Ryanair managed to drive easyJet off these two routes I could expect Ryanair's fares to increase. That's in the nature of markets.