We went with Ryaniar in May to Portugal; I can't fault them to be fair, the seats are much more spacious now there is no 'pocket' in front, much more space than when we flew a few 'budget' Asian airlines last year.
We booked our Ryanair tickets (through a good broker), arrived at the airport in time, checked in - we were allocated seats there and then (even though we didn't pay for that) and weirdly were given the 'fast track' check in at the departure gate. The only difference this was is effectively a shorter queue, but it is not managed and nobody checked, so it may have looked like we just pushed ion, but ah well! Anyway, point is, they allocated a seat on check in - I just assume they have to do this now? I wouldn't bother booking and paying for a chosen seat, just arrive at the airport two hours before, as normal.