I've flown four times with Jet2 ex MAN. Check in staff & cabin crew have always been helpful & cheery, far more customer friendly than many other UK operators I could mention. All flights on time.
Also flown on the MAN -EDI route which was about 50% full both ways, that's not bad for the first week of ops. The EDI aircraft was a combi & showed its age a bit. At the front, noise from the air con and / or door seals made the pa announcements almost inaudible. Mid cabin was OK.
They seem to have launched the more difficult routes first, but I'm sure once the full Spanish/Portugese/Italian routes get going they will be fine.
BTW they don't charge extra for exit seats like Monarch & Baby.