This arguement about Ryanair service (good or bad) as based on wide ranging opinions is debated almost daily on the Ryanair thread.
There is absolute pros and cons for using Ryanair and they have a reliable track record, the big issue as I see it is that they have developed a reputation many markets eg BHX for coming in challenging the competition often removing the competition and then cutting back.
Any time I have used Ryanair it has been a shiny new 737, on time, a low fair, carried on my travel bag and all went smoothly.
They have the lowest fares in the market that it true, but they also have some of the highest fares based on when you book, ie to fly today it can be cheaper to use bmi/Aer Lingus. So depends what way you look at it.
There was an interesting look at Ryanair on Watchdog the other night and to be fair Ann Robinson gave a balanced view of Ryanair. She had a I like Ryanair group and a I hate Ryanair group.
It seemed clear that the passengers who are in the know about the charges and conditions had a good trip, the less well informed ones were less then impressed. However, it also seemed clear that Families felt that a Ryanair flight was pricy owning to carrying additional luggage, buggies and car seats etc.