Really powerful and flexible
I'm really happy to have found such a powerful tool:
I'm working in Biocomputing and I'm used to deal with huge graphs (100000 nodes) to represent biological behaviours such as metabolical pathways.
It's also really easy to implement ad-hoc layout/graph management plug-ins to focus on what really matters to oneself.
The tlp format is something we've been waiting for years: as flexible as XML, but far more compact and cleverly designed.
With the efficient memory management, it's also really easy to manipulate many graphs at once in order to compare them, like in molecular 3D structure comparison.