In the half-year since it was released, this blog has offered both deep praise and, I like to think, withering criticism of the iPhone. On the plus side, I've hailed the iPhone for making the Internet truly mobile. I've docked the phone, though, for being closed to outside apps, and I've cautioned people against buying one until Apple offers faster, 3G wireless networking.

But there is one aspect of the iPhone that neither I nor other observers have yet to fully pause to praise. We've mentioned it as a mere bonus, but have not really considered that this is possibly the most revolutionary thing about it: The iPhone keeps getting better.

Six months after you purchase most any other consumer electronics device, it begins to look obsolete compared to the competition. In contrast, the iPhone you bought last June is actually better now than it was back then.

At Macworld, CEO Steve Jobs put out a trove of new iPhone features, including a clever Maps application that pinpoints your current location. Everyone will get these features through a software update. The additions need no new hardware.

Apple ginned up the current-location trick using a mix of server and client software. The iPhone picks up signals from known cell towers and Wi-Fi base stations, then checks those signals against a database to find a latitude and longitude for each of them. It uses those numbers to determine where you're standing.

Apple also revamped the phone's home screen and added a way to send text messages to multiple people.

Here is the fundamental idea: The iPhone is mainly software, and as long as Apple keeps improving the software -- which Jobs suggested it will, and for free -- your device will stay on the cutting edge. In a short while -- when Apple releases an SDK to allow developers to create their own apps for the phone -- you'll have even more programs with which to improve the device.