1. Primarily, to get where I want to, when I want to. Comfort and convenience of airports are, well, luxuries. I make the call at the time of booking as to whether or not I want to buy them (by travelling on a different carrier).
2. Well, Ryanair are short-haul, and European short-haul rarely has IFE, so I only take the food/drink service as the comparison. For leisure flying, I couldn't care less. Most FSCs' food, I don't bother with, as it usually consists of a sandwich I don't like (why do they put mayonnaise in everything) and a can of something I don't like (I don't drink).
3. Price and destination. As I live in London, there are few places I want to go to where there's not a good choice of routes. Some more obscure ones are served by Ryanair, and the direct flight may be more convenient (that said, a trip to London City, followed by a transfer at, say, MUC, is more convenient for me than a direct flight from STN). As for price, well, I shop around. Given my leisure travel patterns (weekends away, late booking), Ryanair turns out to be the cheapest about 1 time in 3 (taken in account cost of transport to/from airports). And I'm personally happy to pay, say £10 more to be on an FSC. For business, I don't fly on LCCs unless there's no alternative. As far as I'm concerned, the LCC 'cheapness' has nothing to do with lack of in-flight sandwich and everything to do with lack of contingency. If things go wrong, I want it sorted out there and then. And the deal with the LCCs is: you're on your own.
4. On time is very good compared to LHR (although I seem to escape the worst of LHR - I've only had one delay past an hour in 3 years of weekly flying). Never had cause to complain. As for frequency, well, the places I've flown to with them have been rather obscure. I'm not expecting 7 daily rotations from STN-RHE, for example.
5. 'Meets expectations'. I've never paid much to fly with them, and I don't expect to be treated like I'm in SQ F. In fact, I've had very little interaction from staff other than "here's your BP" and "would you like to buy a drink".
6. I have long legs... And so find it a bit tight. For an hour's flight, it's fine, but I'd think twice about doing a STN-RIX with them. So, well, if I want to be comfortable, I turn up early, get an low SEQ number, and queue to get on for an exit row. Managed to bag one for the last 4 flights I've had with them. I've probably been rather unlucky that all my Ryanair flights have been on their museum-piece 732s, which leave a little to be desired in terms of noise and cleanliness.
7. Well, STN is not that convenient for me. It's not too tricky a journey, but LCY, LGW and LHR are all more convenient. But the cost of getting to/from STN is something I always factor into a journey price when doing a comparison. As for the destination airports, well, I've tended only to fly Ryanair to small airports where that airport serves my destination city (I haven't flown to HHN or CRL to visit FRA or BRU, for example). Generally, my leisure travel patterns are time-limited, Fri-Sun jobs, so this is not desirable for me.
8. It works. Many FSCs could learn from its simplicity, and the ability to change bookings online in particular.
9. Leisure only, but if they fly where I want, and are the cheapest (full journey cost), I'll take 'em.
10. Why wouldn't I? I'm assuming I'll have more free time, and less money than now, so I would be easily able to get the real bargains.
11. My impression is that it's found its niche as the absolute cheapest way of flying. If I'm paying £1 for a flight, I don't have high expectations, and they've proven themselves acceptable every time I've flown. Better for me, however, is their impact on the FSCs. It means I can fly BA and BD affordably for leisure trips, which is something I prefer.
12. Not really. They've found their niche, do what they do well, and are sticking to it.