We'll be taking our lad out of school for three weeks in September, I don't feel guilty about it as we're making sure he will be doing the work he's missing prior to the holiday in the six week break. The price issue is a major factor for us, but both myself and my partner work for two large companies and there are holiday allocation issues at work. It'd be great if we could afford to go out of term time and be guarranteed to both get the same dates, but the reality is much different.
We give our holiday a lot of consideration and we're fortunate that our lad is focused at school, if there were any issues with him and his behaviour/attitude then that would be the overriding factor and he wouldn't miss school, end of story. On the flip side, you could also comment on the number of random 'teacher training days' that seem to be dropped on you at the last minute - why can't these be done in the school holidays?
Whilst I accept that taking children out of school is not ideal, how it is managed by the parents is the real factor in whether the child suffers as a result, and until the travel companies realise that school holidays should not be used as an excuse to add on an extra grand to travel packages, taking children out of school will continue to be an attractive option to families.