Here's an another take on the subject I've read. I don't know enough about it to draw my own conlusions yet, but it may add something to the mix.

The Picts never existed.

This theory is based partly on the lack of extant artifacts, and also on those self-same Roman writings. According to the No Picts theory, they were the same as the other Celts in Britain, and the Romans needed a boogeyman away up north. They were a percieved threat, not a real one.

I thought it was interesting. Partly because it flies directly in the face of "common knowledge," and partly as an example of how little we really know about that time and place.

As to whether or not it's true, that's a much trickier problem. I certainly don't know. I'll have to do a lot more research, and I'm really more interested in the 14th century anyway, at which time it's a moot point anyway