We did this 2 years ago. It's nothing like the virgin experience, seats were cramped, it was noisy, not enough drinks provided. On the return night flight the lights were only dimmed for a couple of hours, there were constant announcements and duty free sales etc - it was impossible to sleep.
However - we were paying for 2 adults and 4 teenagers so the saving of at least £400 per person over the virgin flights was hugely significant. We simply wouldn't have been able to afford to go if we hadn't used these flights so in that respect it was worth it. However, I wouldn't recommend it and I wouldn't do it again.