I'm kind of torn about how to review this.
First, I should say that based on what's already here, this is one of the best kid's RPGs I've ever seen, and even as an adult I'm finding this a lot friendlier and more casual than a lot of games on the market. The same kind of rules set that works great for teaching kids works equally well for low-stress games between friends who aren't looking for a tactical challenge but just want to have the fun of an old-school dungeon crawl without all the math. With a group of adults you can be playing a satisfying game inside two minutes of starting time.
So why only four stars instead of five?
Like I said, what's here is fantastic ... and it's worth it at the price point (even keeping in mind that you NEED one of the accompanying books of monsters). But it feels like there should be more. Not in the sense of more complexity -- the amount that any one player has to think about it just about exactly right.
But there need to be more characters to choose from, a longer list of monsters, a longer list of treasures, an extended example of play, more information on dungeon creation, and ... well, just more of everything in general. This could be handled with supplements, but I'd kind of rather see more of a "boxed set" approach with a player book, a monster book, and individual character sheets.
I can also note that the game does seem to assume that an adult will be running the game. That's not necessarily true (and I say that as someone who DM'd her first red box D&D game at around Dungeonteller's target age). But, again, this falls into the same category of "I want more."
Finally, the usual small comments. Individual PDFs for the characters from the same book would be a good addition. The monster counters are a good idea ... but using an isometric view instead of overhead makes it harder to make them work visually when used alongside actual miniatures. The version of the pixie included in the bundle seems to be incomplete; you can get the full pixie by downloading the pixie add-on separately. Also, using pixel or "cartoony" paper miniatures (Octopus Apocalypse, Battle Studios, Darkfast, etc.) gives a REALLY nice friendly visual to go with the friendly rules.
[4 of 5 Stars!]