Not completely true in my case. I have a new 722K dual receiver/DVR. The closest number listed is 721. It will switch channels, but it won't show the program guide. I haven't tried any of the other controls.
Sorry, I should have been more specific. They all use the same IR Protocols, and normally the same button codes although there may be slight differences. But I am very surprised a 721 is different to the 722. I will have to investigate that.