The problem, of course, is that without anyone releasing hardware for the platform, developers have to rely on taking other handsets and porting the platform to it. In the case of Android devices like the Nexus 7 (which is actually an Asus device), it's root and then install a custom ROM.
In addition to the Nexus 7, the Galaxy Nexus, which was Google's last developer phone (the current one is the Nexus 4), saw a port swiftly done after Open webOS was released.
There is both good and bad news about the Nexus 7 port. The good news is that it works at all, and that Web browsing and wi-fi are working. The bad news is that the port is very feature-incomplete and also has performance problems.
More good news: the developer behind it ported the platform in about a week over his college winter break. That bodes well for future ports, and possibly for finishing the port, as well, although obviously it's finishing the software, and that last mile to completion, that is always the most difficult.
A video of the port is embedded; it is described as being alpha quality.