My view is that the airline have done more than enough for you. The delay was under 12 hours and they found a hotel for you, that is way beyond what most airlines would do. The frequent flier points might be of some use, most schemes allow you to use them for various things, not just flights (cheap car hire, days out etc.). The 40% discount of a future flight would probably only apply to a full price flight, not a cheap internet deal. I think you have done ok and would settle for this offer.