I flew to Spain with them last year, with my 2 DDs, age 6 & 8. I was nervous that we wouldn't get seats together. But flight wasn't full, so we did. However, we went to airport early, queued at gate to ensure early boarding. AND THEN they changed the boarding gate JUST as we were to board - so all the people at the back got to front of new queue, and those of us who were there early ended up at the back of the new queue.
Also - the luggage weight allowance is a few kgs lighter than many other airlines. I managed to keep within it, but was a bit nervous that I might be overweight on the flight home (I was Ok).
Oh, and the quequeing for baggage drop took ages (> 30 mins) - because even though everybody has already checked in on-line, lots of people had overweight luggage...
Other than that - flight was fine, same as any other short haul flight, really.
However, this year, I'm flying with AerLingus, just so I can select my seats the day before when checking in on-line. Price difference was minimum, as I booked early.