Some pros and cons:
There are two minor points: The console is pretty big and the in-page version can’t be moved.
Blackbird is a really small logging framework. No frills, just the basics. So no exception logging, for example. A profiling option is the most complex feature. In the world of the logging frameworks, it’s the iPhone: Nice look and only the useful features. The console is always in page, it sits in one of the four browser corners, it can be hidden and shown with F2.
My main complaint about Blackbird is that you can’t use the mouse to move the console. Also disabling the framework needs several lines of code. A single variable would have been more comfortable.