My problem is, for the Xbox version, the Marketplace page for the game specifically said full online co-op was included in the game. This was up on day one back on August 18. We know that was false, and continued to be false for well over two months, until the patch finally saw release.
I would have been fine with the description saying "online co-op to be patched in at a later date", because that would have been the truth. Why wasn't the description truthful? I don't know, you'll have to ask Eidos for that. One possible explanation is negligence. Another possible, more sinister explanation, is that they knew the description was wrong, but lied in order to sell more copies to people who would not have bought the game but for online co-op. But again, who knows? It doesn't really matter why it was there, the fact is that it was there and it was false.
My points are
1) Don't advertise your game claiming a feature is there when it isn't.
2) Consumers should not have to wait seventy days for one of the advertised, compelling features of your game to finally get patched in.
3) If you promise that something (in this case the online co-op patch) will arrive by a certain date (here, September 28), and it will not arrive by that date, let people know beforehand. Eidos did not, waiting until that day came and went until saying "OOPS sorry the patch isn't coming today", and even then it was through a forum post that was difficult to find.