Most about RyanAir has already been said, but there is one aspect that is yet to be mentioned, and for which I am very thankful to RyanAir and other LCC's - the massive drop in flight ticket prices over the past decade. I am a Latvian who grew up in Stockholm, Sweden, so I have always been flying a lot to Riga, Latvia. It is a very short flight - between 45 and 70 minutes depending on winds and aircraft type. Before the rise of LCC's and RyanAir, it was common for a ticket to cost 3-400 EUR round trip. The same with tickets from Stockholm to Germany - they maybe were a bit cheaper, but still hard to find below 250 EUR round trip. Of course, there were always exceptions and sales, but it doesn't change that the average ticket prices were very high.
Since LCC's and RyanAir stepped up the competition, offering dirt-cheap fares, most other carriers have been forced to review their pricing policies as well. Maybe there are other factors as well, but I do feel that there is a strong correlation between lower ticket prices accross the board (especially compared with the 1990's) and airlines like RyanAir, for which I am very thankful for. For example, for Christmas me and my wife flew Riga-Frankfurt for 40 EUR p/p (AirBaltic), Münster-Osnabrück - Berlin for 60 EUR p/p (AirBerlin) and Berlin-Riga for 70 EUR p/p (AirBaltic). Earlier this year we flew to Belgrade from Riga for around 100 EUR round trip. Before RyanAir, all of these tickets would have cost at least the double amount.
This is what I like the best about RyanAir and other LCC's. If I have the chance, I avoid RyanAir since I don't like the feel of cattle transport which the airline has, but if the difference in price is significant, I'd rather spend my 1-2 hours on RyanAir and waste my money on dinner at a high-end restaurant.
All you have to know that if you fly with RyanAir, obey all of their rules, no matter how silly they might seem, because if you don't, there probably will be an employee looking to get a truckload of money from you for allowing you on the flight. If you do not want that, fly with another airline. As simple as that.