The similarities between K-Meleon and Firefox are numerous, and like Firefox, K-Meleon runs on the Gecko engine as well.
K-Meleon is marketed as a fast light-weight browser. I would have to agree with this. Even the installation is fast and didn't default me to make it my default browser or force any unwanted settings on me.
This is a tabbed browser, but instead of tabs, the terminology in K-Meleon is "layers".
I searched around for other similarities between K-Meleon and Firefox. To do this, the first site I opened was ABS. Even the display issues are the same, but I think it stretches broken images to the size of alt text instead. Also, K-Meleon is so light that it comes with Flash Player 3.0. Obviously, this plugin will need an upgrade to work on ABS.
I got bored of how simple, clean and efficient this browser is, and started looking for advanced features. I found the zoom ability pretty useful, and even though it had the ability to zoom images and text independently, this didn't always seem to work properly. There is no "return to normal size" feature that I can see, so I suggest not messing with the zoom.
K-Meleon didn't leave out any popular advanced features like Javacript console, mouse gestures, favourites importer, domain completion and others. Some of the more advanced features let you edit the source directly rather than a simple enable/disable.
This browser is fairly new, so I'm not sure about automatic updates and its security, but I can assure you that this browser, like all Gecko browsers, are safer than Windows browsers. At least for now.