VIA chips pull little power (most under 20W) so battery life should be great.
Bad thing is the graphics chip that comes with most VIA equipped systems is not very powerful (worse than Intel) and the performance of the chips compared to AMD and Intel aren't the greatest (but, thats not VIAs intention).
Is the video really a big issue? I recently bought an ultra portable that uses a 1Ghz C7 and so far it plays movies ok and i attach it to an extra monitor when i need more room.