I fly 8-10 sectors a month with EZY on average when I'm in Europe, most recently yesterday, and have been doing so for over 10 years. I've only ever had 2 problems, both minor, and one beyond the control of the airline and well handled by them.
Most flights are good, clean new aircraft with tidy cabins and competent friendly crew. The whole experience from booking on their website, through managing bookings, to the flight itself, is exactly as it should be. I often find they arrive ahead of schedule, exceeding expectations.
I also dislike the seating scrum, and have tried Easyboarding or whatever they call it, and find it's a waste of money and effort. As F3G says I don't like free seating either, but over the years I've got used to it and accept it as part of the deal, there's more upside than downside to the airline.
I've only flown Ryanair once, never ever again, and my only other direct comparison with EZY in and out of LGW is Aer Lingus, who are better than EZY, but don't offer the same frequency or variety of routes throughout the year.