I saw somewhere that (now their) App Inventor makes for 13 percent of language use for education purposes, while Python is at 14 percent. They must be doing something right.
This is great. I use it for prototyping app ideas, and it works good so far. Only thing I've found to miss for my particular prototype is a "wait" function, but there's ways to build a little procedure for that.
(Also I submitted AppInventor to HN a while ago [1], but it didn't get any attention. Bad timing maybe? Either way, I think it's excellent in it's simplicity)
http://appinventor.mit.edu/