As one of the creators of Arduino (and currently its lead software developer), I'm happy to see such a lively discussion of the platform. I'd also love to hear any suggestions you might have for improving it.

I should note that we've done very little promotion ourselves, apart from teaching lots of people to use it in various workshops. Of course, we're happy that Make is such a fan.

One interesting feature of the platform that hasn't been mentioned here is the fact that the whole thing (hardware and software) is open-source. We've had lots of people take the Eagle (CAD) files and design their own custom variants, which creates a vibrant ecosystem.

Finally, if anyone wants to get involved and help make Arduino better, check out our developer pages at: http://code.google.com/p/arduino/