I completely agree with you. You would have assumed that Sonos would have been equally aware of (1) and (2) and factored that into the product's capability. It seems simply too early to release a product that relies purely on the optical capability of TVs. I wasn't told about this limitation during the buying process, and no doubt the same applies to many other people.
My only alternative to this system was proper 5.1 separates, but with small speakers (such as the Minx). However, I wasn't that impressed by the sound on test, and once you factor in the cost of the wiring and chasing cables into the wall, such a system would not have been much cheaper (if at all) than the full Sonos system. The larger speakers of the Sonos, and their wireless nature, therefore meant they appeared a hugely attractive option (including for keeping my wife happy!). I am still happy with the choice, the surround sound on Sky HD is very good to my ears (although I have never had a full 5.1 system in the house with which to compare it), music abilities are excellent and if I can improve the Bluray player's sound to that same degree then all the better. Thankfully, I don't have many Blurays already!