Once the four devices are identified, the system automatically downloads the correct codes from Logitech's massive database ("more than 225,000 devices from more than 5,000 brands," according to the company's press release) to the remote, which connects to your computer with the supplied USB cable. (The remote has a standard mini-USB jack, so it's easy to find a replacement cable if you misplace the included one.) By contrast, other universal remotes in the sub-$50 price range usually require you to go through a frustrating trial and error procedure of inputting numeric codes and verifying whether they work with your device.
On the off-chance that you have a new or obscure device that isn't (or isn't yet) in Logitech's database, the software will guide you through the "learning" process. It basically involves pointing an existing remote at the bottom of the Harmony 300--where an infrared (IR) receptor is housed--and tapping the requested buttons so the Logitech software can absorb and assign the appropriate IR commands.
The software handles two other functions. The first is customizing the button functions for each key on the remote. Many of the obvious keys are preprogrammed by default (play, pause, numeric keypad, etc.), but you'll still want to personalize things to your liking. You can do this on other Harmony remotes, but the new software makes it easier and more convenient than ever. Using a graphical version of the remote on your PC screen, you can simply drag and drop functions for each device to the corresponding button. Specialized buttons for set-top boxes or game consoles (such as aspect ratio or the "A," "B," "C" buttons found on many cable-based video-on-demand systems) can be mapped to the colored buttons in the center, or the five numbered keys at the top. It's about as simple and as intuitive as it gets. The software also lets you assign "punchthrough" commands for volume and channel buttons, such as always designating the TV to control volume and the cable box to control channel changes, even when another device is selected.
The second software customization is preparing the "Watch TV" macro. Using the software wizard, you let the system know which devices need to be powered up and set to which input so you can watch TV (e.g., TV on, switched to HDMI 2 input; cable box on; AV receiver on and switch to HDMI 1), giving you a one-button way to turn the system on. (If your devices use identical power on and power off codes, the "Watch TV" button will also shut everything off; otherwise, you'll need to power down each device one at a time.)
This is the sort of automatic activity-based programming that Harmony remotes are known for, but on the 300, it's limited to this single function. If you want more ("Listen to music," "Watch DVD," "Play video game," and so forth), you'll need to upgrade to the Harmony 600 or above. Likewise, if you've got a remote with a large number of specialized buttons, the Harmony 300 isn't your best choice. And, with any universal remote, the normal caveats apply: you'll need good line of sight to your gear's IR receptors, and the automated input switching won't work well unless your products have discrete inputs (most TVs and receivers from at least the last five to eight years should).
We programmed the Harmony 300 to control a Panasonic TV, Scientific Atlanta DVR, JVC AV receiver, and Sony PlayStation 3. (Because that last product doesn't include an IR receiver, you'll need to invest in the Logitech Harmony Adapter for PlayStation 3--it works perfectly, but costs more than the Harmony 300 itself.) The Harmony 300 performed flawlessly, working just as well as previous Logitech models we've tested. The IR emitter is quite powerful, and as long as the remote was pointed in the general direction of our gear, there weren't any missed commands. We also liked the general feel of the remote as well. Yes, it's a bit large--you'll either need to shift your grip so your thumb can swipe farther up or down, or you'll need to go two-handed--but it's as good a compromise as you can get, given the overall button layout and the number of keys available.
Our biggest beef with the Harmony 300 is the same frequent complaint from past Harmony models. There's still no way to organize multiple remotes under a single online account, so you need to use separate e-mail addresses for every Harmony remote you own. With Logitech now producing models specifically designed to be the second and third remotes in the home, we continue to hope that the company figures out a way to organize disparate remotes under a single account.
That quibble aside, there's a lot to like about this remote. To reiterate, the Harmony 300 isn't designed for a sophisticated home theater system. It only controls four devices, has no LCD screen, and lacks task-based commands (beyond "Watch TV") as well as sophisticated macros/sequences. But Logitech (and other manufacturers) make plenty of more-expensive models that cater to those needs, so we don't count that as a flaw. We have no problem recommending the Harmony 300 for TV-based entertainment systems in a bedroom or den (say, a TV, cable/satellite box, DVD player, and/or game system). It allows you to ditch up to four separate remotes, and it offers the easiest PC-based programming procedure we've seen to date.