My mouse can control ANY device in a home theater system. DVD player, amplifier, HDTV display, cable box, sat box, and anything else you can think of. It cost me a whole $50 for the IR transciever that the system uses, wow. Its not specific to the Logitech mouse, I used to have a Microsoft wireless intellimouse explorer and it worked just as well. Its a pretty simple concept to understand, the software I use simply maps the mouse buttons and/or keyboard keys to IR signals based on the AV device I am currently watching/using. If I switch to a different AV device, the mouse button mappings change accordingly. Navigating an AV device menu is a thousand times better than it is with the stupid up/down buttons on a remote since it uses the mouse scroll wheel for that. Anyone with a cable box can relate to the huge difference that would make.
As for using an IR remote to control my HTPC, I can do that as well, but I can use ANY remote I have laying around for that, and all I need in that case is my IR capable wrist watch. :) When I press the button on my watch I have specified to be Play, Pause, Mute, etc, the software detects which application I am using, such as Winamp, Windows Media Player, Media Player Classic, etc. and issues the correct command for that application. Its not something I use a lot for my HTPC, since the mouse is always right there for that, but it is VERY important for my carPC.

Your right that it is not "on par" with the top tier remotes for HTPC and home theater control on the market: it leaves them all so far behind its ridiculous.