Argyle & Crew is a very basic set of guidelines for running storytelling games. Since there are no limits to what the Extras can accomplish, it can be very easy for the players to achieve the Goal very easily. It's up to the Guide to make sure that the story remains interesting for the other players, and this can be a real challenge. The rules suggest a "There is only yes" guideline, in which the Guide attempts to answer all questions and requests with "Yes" as often as possible, except when it would involve short circuiting the story (such as letting the players jump directly to the Goal), hurting or being mean to others, or passing any boundaries or limitations that were previously agreed upon.
Personally, I would suggest using the "Yes, but..." method, which gives the gamemaster the option to put a restriction on the request. ("Yes, you can use your pogo stick to jump to the other side of the island to get to the Goal, but once you land there, you find that someone has moved it!")
Some advanced rules near the end of the book turn the game into something a bit more like traditional RPGs, with numbered stats and d6 rolls to determine results - these may make the game a bit more appealing to older players and Guides who would like to work with something a little more concrete.
The published scenarios for the game have a general theme of coping with social situations - bullying, for example - and it would be great to see more of these released.
Argyle & Crew is a great introductory storytelling game that will work well with younger players, and could have a lot of potential in teaching environments. The physical element of the puppets will draw lots of players in, no matter their age - who doesn't like playing with puppets, after all?