Interesting, I had a comp case with BA but it was very easy. Likely because they were clearly at fault (mechanical failure) but all I had to do was fill in one form and I had my money 3 months later.

I think the experience is circumstantial and definitely depends on how 'obviously' in fault the airlines is. All in all I came out with a profit of £200 but can't say 24 hours at an airport is worth it honestly.