Leo and I worked together in two projects involving web technologies. I've never worked with him before, but I instantly knew that he loves what he does. Leo is a very passionate person, and he is capable of transmit you that feeling. Even when we faced problems, he always showed me the "good side of the coin" and fixed everything.
When he encounters a new challenge, he just analyzes every possible situation and choose the best; even if it's an unknown solution for him, he is not worried at all because he loves to learn. If you are looking for a commited, good and "fearless" developer, Leo is your guy.