Obviously, the situation rapidly went beyond an adventure for those with broken travel plans, but from what's been reported I don't think anyone (other than Michael O'Leary, of course, full of insufferably arrogant hot air as usual; and profiteering companies in fields such as car hire) has been unreasonable. It's impossible to get things absolutely right in a changing situation, and it was plain that the moment the Navy was sent in to collect people, it would be too late and planes would start flying again.
Planes haven't started flying because the ash cloud has cleared (though it has dispersed somewhat), but because the goalposts have been moved. Whether that is a reasonable course of action remains to be seen. Channel 4 News reported that a cargo plane landing in Ostend had ash in its engines, with further examinations to be carried out. Two of my co-workers are due to fly on holiday tomorrow, and though of course nothing compared to those stuck away from home, it hasn't been much fun for them this week either.
nwhyte has linked to a couple of interesting articles here. One of the things that does seem to be a fair target for criticism is the reliance on a single computer model; but then again, having multiple computer models wouldn't do much for "efficiency savings", would it?