I saw David Chernushenko at an all candidates thingy last election, and yes he is a good speaker. The interesting thing about Ottawa Centre is the fact that it a fairly well-to-do riding, and smack in the centre of Ottawa. It was Liberal for a long time, but went with the NDP with Broadbent. I think Dewar's win shows that was not necessarily a flash in the pan (although Dewar is the son of a former popular Ottawa mayor). At the same time, Mahoney was closely identified with Martin's inner circle (he's also kind of full of himself). Either way, this is a riding where urban issues play heavily.
I have big questions about the Green Party. I find that some of their policy suggestions a bit weird (sending the military to deal with environmental issues), and they make rather broad statements concerning environment and health that are not necessarily backed up by any science.