Matt to my knowledge is an intuitive and creative investor (he invested in Memrise on the basis that he thought the world would be better to include such a service). As a mentor, he's generous with his time and unusually clear-minded with his advice. This advice, if one can even call it that, typically comes in the form of deceptively simple questions that cut to the heart of what you're trying to accomplish- an almost philosophic gift for asking 'why'?.
With such a range of experience and such a subtle and enquiring perspective on that experience, he's an exquisite resource for any startup. Also fun. Very fun!
First off, if Matt wants to invest in your company the only answer is "yes, absolutely." If you need a little more convincing, I will say that he's been one of the most helpful investors I've ever worked with in my career. At Circa, he's made two major commitments and has been an absolute pleasure to work with. If and when I have another company in my future, I would no question jump at the chance to work with Matt again. You literally can't get a better angel.
Matt is my favourite investor. He makes time and offers thoughtful and patient advice when needed. He is a truly good person who appreciates the small things in terms of good software and good culture. At the same time, he knows how to scale a company and change the world. Matt is my hero and I'm honoured to know him as an investor.