In reply to Confused Chimp: I tend to strip down my climbing rucksack so I can use it as hand luggage, and then take a bigger kitbag as hold luggage. It's nice to have a sturdy waterproof kit bag.
Having said that, I've not had a problem with rucksacks in the hold getting damaged, but it is quite a pain having to sort out all the straps and putting them through as over-sized/fragile luggage.