I've taken around 35 or so flights with Ryanair over the past few years...and took them to Ireland for Christmas last year which was fine. In my experience, I've usually found:
-Ryanair are fine if you play their game, read the small print and adhere to their policies. Their baggage policies are pretty strict but they enforce them different at different airports. For example, at Glasgow-Prestwick there is a scale to see if a carry-on is over 10kg, but in Berlin they're concerned if it fits in the cage and it's the size that is important, not the weight and in Edinburgh last year there were no checks at all for weight or size. It's really confusing. I was 2kg over once and had to pay £35 (I couldn't throw anything out sadly) but that was my fault I guess. And since I had paid £8.99 with tax for my flight I wasn't really terribly bothered.
-Non EU citizens have to have the 'visa check' which no other airline really does...it's pretty easy, you just pop over to the dedicated desk and get a cheesy Ryanair stamp on your boarding pass.
-Onboard food is quite pricey, get some snacks in the airport if you can!
-Announcements are made constantly (food/drink, duty-free, scratchcards, smokeless ciagrettes, phone cards, and transfer bus passes to name a few) and on a few occasions they woke me up to see if I wanted to buy something lol.
I've never actually been on a full flight, but whilst I prefer EasyJet, I would have no problem going with Ryanair again, especially on a short flight. I think the worst-case scenarios occur when they can't operate a flight (either because of a strike, weather related issues, etc) which is outwith their control and you get stranded in a random secondary airport in the middle of nowhere. If you're going to visit family, presumably you'd have a place to stay if that happened and it's very unlikely anyway, but I think that's one of the main complaints. I've personally never had that happen, once we were delayed a few hours in Liverpool but that was about it.
They used to have an annoying 'theme' song they would blare after takeoff sometimes but thankfully this has ceased lol. It got stuck in your head for ages!
Ryanair has really opened Europe up for me, I actually *have* in the past, got flights for 50p or £1 each way with tax, so it is possible. Anyway, as long as you're not expecting much you will be pleasantly surprised. I do prefer Easyjet as they seem a bit more professional in how they handle customers, but would take Ryanair if the price was right and they went to where I wanted to go.
BTW: here's a song about Ryanair I found pretty funny (be advised that there is a bit of strong language in it, but it's SO true!):
FASCINATING AIDA - Cheap Flights