Only caution I'll give you about using Air Video is this quote directly from the app description in the App Store:
"Air Video will not play DRM protected videos. All video content purchased through iTunes includes DRM. Video podcast content is free and does not include DRM protection."
So, for your iTunes purchased video, I'd say no, Air Video will not work for you (well, on THOSE particular videos).
I also don't know of another streaming app that'll work well not over your local WiFi/LAN. Maybe Splashtop will work for you (definitely while at home ... not sure how to set it up for outside the home)? Or some of the other remote desktop apps?
Or, you could wait to see wait Zumocast comes back with ... as they are supposed to return in a couple of months. I have the app and I must say, I am glad I do as it works great.
Or, look into the new Air Stash? It's a $99 (USD) device that'll allow you to stream videos/pictures/etc. wirelessly (over its own WiFi network) to your iPad. I have my eyes on this myself. Just waiting for a bit - they are supposed to be coming out with an app to make it easier to use (but, if you get it now, you'll get software updates from the vendor).
Mainly, just wanted you to be aware of the Air Video limitations on iTunes purchased and/or DRM videos. Sorry to ramble on about other things...
Marilyn