I flew RyanAir once to Ireland and it was fine: no delay, no bad attitude from staff. However, I found the constant advertising by the flight staff very annoying as the entire flight was taken up with them telling us about such-and-such offer (raffle tickets, perfume, etc). Yes, EasyJet does the same thing but not literally for the whole flight.
The other irritating thing about Ryan Air, while cheap, wasn't nearly as cheap as you initially think. I decided on them over Aer Lingus because the advertised price was cheaper but in the end it was exactly the same price as Aer Lingus. The price you see advertised on page 1 will be very different from the price you pay on page 8 payment processing page, even if you uncheck all the extras. For example, they will charge you to check in at the airport (something you must do if you are not an EU citizen), they charge you to book online, they charge you to use a bank card, credit card for payment, etc, etc. At least with EasyJet, you pretty much know what you'll pay from the get-go.
Also, while RyanAir to Dublin is fine, in other parts of Europe, RyanAir flies to secondary airports so be careful when you book your trips that you are actually saving money. For example RyanAir advertises flying to Barcelona, but it actually flies to Girona, an airport well away from Barcelona proper. It will cost you much more to get to Barcelona (and time) from there than it would if you flew EasyJet direct to Barcelona airport.