There are plenty of downsides to Ryanair as to just about any outfit. The major upside is the probability of continued employment.
You can cherry pick better terms and conditions. By all accounts Easyjet is good for those with an established career as is Lord Spandex Monster's mob if you are not on a seasonal contract. But you need to be in the right place, Dortmund and Madrid spring to mind as far as Easyjet is concerned.
For Ryanair contractors based away from home unsure about tax and needing a regular income it is certainly not all positive.
Equally if you factor in possible upsides e.g time to upgrade, likelyhood that the airline will still be around in five years etc. then the numbers are not bad for example when compared to Air Berlin. There is no shortage of other shaky candidates.
I suspect there is a vast silent majority who are perfectly happy. Although to be honest most of us love to have a good moan.