You know what, I haven't ever watched it. Always have wanted to but its one of the series that I feel the need to watch right from the beginning. I wish it was on Netflix. I might just buy the first season.
Ya it's a really good show. It sucks that it isn't on Netflix though. If you have Bell and the Movie Network On Demand, all six seasons are there and there aren't any additional costs to watch any episode.
It's definitely worth watching, but it is good to start from the beginning.