You can't legally use the video marketplace and Zune marketplace, but as far as I know there are simple workarounds to bypass the IP region filter.

Do get a US Xbox live account if you're planning to purchase vids over you box. I've got a SG acc and I wished I had registered for a US acc instead. I'd jump over but I don't want to lose my gamerscore

I've seen some guys over here use netflix on their 360 so they might tell you how to get it done.