More Portal is never a bad thing, especially if you've done everything you can possibly do in Portal 1 and 2. One of the best things about Valve games is the degree to which they can be modded—and the quality of what their fans can produce. Maybe they're hoping to get hired by Valve themselves once the company sees what talented devs they are (hey, it's happened before).
What other Portal mods are you into? Give us your thoughts and impressions in the comments or on Twitter.