Pros
You can live in many interesting places. You can live in a country without knowing its language and learn there (Ryanair doesn't require other languages than english). It's relatively well-organised airline - good maintenance, not much mess with delays, cancellations, crew being out of hours etc. Good general and safety training. It can be a good experience at the beginning but I don't advise staying in Ryanair longer than a year or two.
Cons
Very poor conditions. People do not matter for Ryanair. As long as there will be anybody willing to work for them, their approach is "if you don't like conditions, nobody stops you here". Juniors get paid only for flight hours with pax onboard (I had once a day 3pm-7am for which I got paid nothing). Quite bad organisation culture, that supports reporting your colleagues, big salary and perks difference between juniors and seniors. New contracts are always worse that the old ones and you're forced to sign a new contract when you want (or have to) change the base. The company is very sales-oriented so there are various sales targets and supervisors are unhappy if you don't reach them. Deal is simple - you got job to do and you earn money when you do it - nothing more, nothing less.