Although something needs to be done about airlines that avoid their responsibilities with compensation when people have bothered to claim any (legal action by the individuals concerned would be a good start) I tend to think these no win no fee claims companies do a bad thing and ultimately will saddle the frequent traveller with more costs just like those personal injury claims companies (e.g. claims direct) have pushed up car insurance fees in the UK.
As I know the rules I always claim compensation for delays and cancellations whether it's rail, air or tube but I suspect if everyone bothered to do this we would see fare rises or in the case of air travel yet another 'tax'. I've actually been fairly lucky with travel with KL, never been in the situation where I've been delayed so long that I'd be given any actual compensation but I've got the voucher book a few times which gets you 2000 miles if you don't redeem it for food.
Swiss is the only airline that has been obliged to give me compensation for an involuntary denial of boarding but they did that without any hassle.