I'll go first:
I've flown Ryanair a few times, from London to Graz, Trieste to London, and Rome to Dublin.
First trip - Our first flight was back in 2001, and went without a hitch. Ryanair wasn't charging as many luggage fees back then, so that was nice. Flew out of Stansted, which was no further than Heathrow for us, and the shuttle was a lot easier than hauling luggage through London to the Heathrow Express.
Our eventual goal was Vienna. I wish (at the time) they flew somewhere closer, but the train ride from Graz to Vienna is stunning.
Second trip - Flew from Trieste back to Stansted. Flight was delayed 2-4hrs, but nothing worse than I have experienced with any other airline. The shuttle from Trieste wasn't great. (There is a full sized bus I wish we would have taken). But the amount of money we saved vs other airlines ($400) was worth it.
Third Trip - 2009. Rome Ciampino to Dublin. Ryanair's rules have gotten a bit more restrictive, but we researched in advance, and were prepared. We paid the extra couple dollars for pre-boarding which was nice and well worth it. We got hungry and ordered some food, to my surprise, it was quite a good sandwich for 5EUR!
Ciampino was a wonderful airport. I LOVED having to go through there rather than FCO. It's a small(er) airport, and was much easier to get around. We flew directly into Dublin(DUB). Which is of course the main airport, and baggage was out quick, and we were on our way. The taxi ride to Ciampino from our apartment was actually 1EUR cheaper than FCO, and was about a 40 in drive through some beautiful areas.
By all means, if any of the major airlines were anywhere remotely close on price, I would go with them just for creature comforts. But we've never had a bad experience on Ryanair, and never been charged an extra fee.
In contrast: On those same trips our SAS flight sat on the TARMAC for 3.5hrs (before a 9 hr flight), and the British Air flight was 17 hours delayed.