I have successfully taken legal action against KLM and Easyjet (for myself) and Ryanair (for a relative), I think I know the EU regs fairly well now. I suspect you won't have a strong case since the flight did run - just very late, which is currently deemed ineligible for compensation. You also allowed yourself to be rebooked, which complicates matters a bit.

The precise details will matter, but I think there's a general point to be made here: Going down any legal process will take a lot of time and letters, and a bit of cost - hopefully recovered. I would only do this if I had a real sense of greviance which the airline did not properly address. Truly life is too short to get into legal manœuvres, as a general rule - think what else you could do with the time.

In your case I perceive that BA's pro-active management probably headed off too much of a sense of greviance developing, which is actually good news. In my experience BA are good at paying off the "duty of care" elements. I once submitted a bill, which involved an overly expensive meal during the delay (£80 from memory). I clearly crossed it out with a note of explanation, BA paid it anyway. I'm also a shareholder so I had mixed feelings about this!

My perception is that you are then left with what is the right compensation - in a broad sense - as to the inconvenience and loss of enjoyment. You have to ask yourself this, in a very honest way. Mere loss of time is probably beyond quantification, and indeed do you want to waste any more with a long paperchase with BA Customer Service. How much of an inconvenience was it really? Was there something you were planning to do which could not happen? Was an extra night in Chicago a good thing or a bad?

I also take the view that BA don't want these things happening, and so they will do everything they can to avoid this. You may also want to factor into your mindset what else BA could have done - namely put you on the delayed flight, and/or in CW, or on AA. This may also work to BA's credit?

So in your shoes, all things considered, if I got 10,000 Avios (and my experience is you will get more), which would get you a nice mini break in Europe; plus the £40 you presumably are getting from your travel insurance with which you can have a nice meal; along with a letter of explanation and apology - then this would satisfy me. Your stance on life may be different, but then we're all different, thank goodness.