The best tidbit about this update, you can now download demos to your DS from your Wii and play them from this Channel. I tested out the preview for Brain Age 2 and Ninja Gaiden: Dragon Sword this weekend, fun games!
The official "Nintendo" blurb about the "Nintendo Channel"...
The Nintendo Channel, the newest Wii Channel, is an interactive guide to what's new in the world of Nintendo - and it is available for easy download to your Wii from the Wii Shop Channel. Watch trailers, mini-documentaries, product demonstrations, and gameplay videos. Gain useful information about your favorite games on Wii and Nintendo DS from reading the game guide pages. You can even click to buy straight from your Wii.
Information about Nintendo Wii updates is available here.