Really nice intro. One comment I would make for a follow up video is that your bit on setting up tokens should really show the strengths of linking tokens, and the wealth of pregenerated monsters available in the Compendium. Also, the setting of Default Tokens really trips a lot of beginning players up.
By all means, creating an Ankheg token is important, but going the extra step to show your viewers how they can drag a complete Ankheg, ready to go from the Compendium, and assign your custom Ankheg to it is a vital strength of Roll20.
Also, the trick of keeping monsters on a "secret page" pretty much duplicates the purpose of the GM layer. Is there a reason you feel this is a superior method?
Other than that those last two bits, the rest of the video is very solid and clearly presented. Nice job!