The Logitech Harmony is the ultimate remote control.
Let us take a look at the evolution of remote controls, so that you can fully appreciate the dizzy heights that the Harmony represents.
Phase 1: Look, no wires!
You have a television set which can be controlled remotely! Your fancy infrared remote control is wireless, which is practically magic. Your television is fully self-contained, since digital cable has not been invented yet, so you are perfectly content with your remote.
Phase 2: Which one turns on the cable box?
Your television now has a VCR and a cable box plugged into it. You own three remote controls. This is sort of fiddly, and clutters the place up.
Phase 3: Universal Remote
Your "universal" or "learning" remote has taken on the roles of the three remote controls you used to use. This is great! At the flick of a switch, your universal remote can control the VCR, the TV, or the cable box. Your friends are astounded. If your universal remote is really fancy, and you have time to spare, you can even program it with "macros" to e.g. turn on the TV and the VCR at once.
Phase 4: Home Cinema Revolution
You now own a flatscreen TV, two video games consoles, a surround sound amplifier, eight loudspeakers, a blu-ray player, a cable box, and a TiVo. Watching a movie requires you to turn on three separate devices, and set the correct input channel on two of them, if you can even remember which the correct input channel is, because your amplifier doesn't have a slot labelled "blu-ray" and you had to use the "LD" input, whatever THAT is.
If your wife wants to watch a soap opera, she calls you into the room to turn everything on for her. There's no way that your humble "universal remote" is going to help with this.
Phase 5: The Harmony
(Imagine a kind of angelic chorus sound at this point)
Enter... the Logitech Harmony remote.
Your remote has a button labelled "Watch blu-ray". You press this single button, and the remote switches the TV on, and the blu-ray player on, and the amplifier on. Then, the remote switches the TV to the correct channel, and the amplifier. You are now in "watch blu-ray" mode, so all the buttons on the remote control the blu-ray player, the TV, and the amp, as appropriate.
Some time later you decide to play video games. You press "Play Xbox" on the remote. The remote switches the Xbox on, leaves the TV and the amp switched on because it remembers you were already using them, switches the blu-ray player off, and switches the TV and the amplifier to the correct channel.
What if your cat jumps on your lap and blocks the signal to the amplifier? No problem, hit the "help" button on the Harmony, and it will attempt to automatically rectify the problem, and then if that fails, prompt you with a series of questions until everything is working correctly.
Obviously, you must first configure the Harmony. Configuration is accomplished by connecting the Harmony to a Windows or Mac computer, and following the instructions in the Harmony software. Logitech maintain a truly vast database of devices, so it's likely that your TV, amplifier, and so on, however old, will be "known" and configuration will be mostly automatic. If you have an unusual device, though, the Harmony has a remote sensor and can be "trained" from your existing remote.
The configuration software is easy to use. If anything it's over user-friendly, and technically-minded people might prefer a little less hand-holding. That said, it's still very flexible, and allows for weird configurations, like my two-amplifier setup, and custom commands. If things go wrong, it has a detailed trouble-shooting mode that lets you configure ultra-detailed settings like tiny delays between commands, or the order that devices are switched on. Really, it feels as though you could make it do anything you would reasonably want. Reportedly, the phone-line technical support is very good as well, although I have not had to use this.
In summary: if you have a home cinema setup of even average complexity, you want a Harmony remote. Particularly if you share your home with someone who, not unreasonably, just wants to be able to watch Antiques Roadshow without having to follow an instruction sheet.