A great idea... On Nintendo's part.
Gameplay- 6/10
This is the part that could have used the most work. I like how you could draw as well as text, but I would have liked to see easier access to smileys. Another thing I hate is how when you drag a letter up to the pad, you can only type in that spot. I'm not saying that it's a bad idea, it's just that if you are typing fast and you slip the stylus from one letter to the other, the game won't pick up that you typed that letter, thinking that you were going to drag it, but then decided not to.
Graphics- 7/10
I love the style, but they could have used a lot more customization to the drawing portion. All that you can do is change the width of the lines you are drawing with. *yawns* I would have liked to see color, fill-ins, and some preset shapes that you could insert in. I know about how many art-inclined people have started to "paint" things on Pictochat, and I think that is very neat. Sadly, I am not one of those people, so I don't really have any comment on it.
Sound- 5/10
The only real sound in this game are the dings of typing and the dings of receiving messages. That's it. I would have liked to see some sounds that you could send from player to player.
Replay- 3/10
I, personally, I have not played this game all that much, so I wouldn't know much about this factor, but I really couldn't see you playing this game all that much since you need at least one other person, and with DSpeak on the horizon, that would probably replace Pictochat. Don't get me wrong; if you have a lot of friends with DSes then you might use this a lot. It's just that I don't.
Overall- 6/10
Again, I say that this has a great concept, but is lacking in content. If you have a lot of friends, you might love it. Either way, it comes with the DS, so I can't really urge you to buy/not buy it. I hope this was helpful!
~Cap'n