I like woopra too and I just checked out clicky's demo page. Clicky is really nice. But if I were to compare woopra to clicky, I think woopra has a nicer interface/visualization. They just did an update yesterday on their web interface and its now almost as good as the desktop client.

I use three analytic and all of the them are free. I don't use woopra anymore, but I will probably use them if I am looking for a commercial solution. Clicky seems to have more customized tracking solution and looks like a better solution for people who are looking for a more in-depth tracking data.