Currently Skype on the N810 does not support video calling. This is a Skype issue, and not Nokia's or Maemo's responsibility, since Skype is developed by, well, Skype.

You *can* use Gizmo Project with video for tablet-to-tablet and tablet-to-pc video calling. I've done both myself and it works great.

Skype on the tablet is indeed free for Skype-to-Skype calls. The extra fees are for if you want to be able to dial out to non-Skype contacts and such.