I got the teal colored pen, with a medium sized nib. It came with a black ink cartridge (one that only fits Pilot pens), a
The pen writes well enough, doesn't skip, and isn't too scratchy. It comes in different colors and different nib sizes. It is cheap enough to buy on a whim, and you won't lose any sleep if your kid happens to bend the nib, use it as a dart, or trade it for a not-so-rare Pokemon card.
I was going to describe the pen in more detail, but then I found a much better review with great pictures, all of the specs, and even a video. I hope the folks at Gourmet Pens don't mind the reference: Pilot 78G Review. Oh, and here's another good review at Ink of Me Fondly: Another Pilot 78G Review. The pen in the first linked review has a broad nib, and the pen in the second linked review has a fine nib, in contrast to my medium nib.
The first sample also includes short blurbs written with other fountain pens that are described elsewhere on this blog, just for the sake of comparison.
The bottom line with me and the 78G: it's well worth the price and is a decent pen, but I'd rather use my Pilot Custom Heritage 91. In fact, I gave the 78G to my son for use as a school pen. I would recommend the 78G as a "first real fountain pen" (rather than, say, a Pilot Varsity, a Platinum Preppy, or a Lamy Safari).