Yes, but your question of "works well" is a good point. I should have added more to my first post.
@Michelle M -- Having all leads register through a Marketo form is the better way to do the WebEx integration, to guarantee that you capture everyone in Marketo from the beginning, and to ensure that your Marketo emails and programs execute the best (if that's your goal).
But leads who register for the webinar via another medium will still be synced into Marketo if they attend. So while not required, you could likely miss some leads by not doing registration through a Marketo form.