I think they are growing and are a small but positive influence right now. That influence, if things go in Canada like they have elsewhere, will become much greater in a relatively short period of time. They are as much a world-wide movement as anything else, with substantial political representation in many countries.
They are also not communists. Their leader is an ex-tory, so statments like that are just silly, really.
My biggest problem with the Greens is that they may take votes away from the NDP, since they draw more from the left side of the political spectrum. They do draw from across that spectrum though, and many people who would not have otherwise voted do support them.