I saw the letters discussed in a report on CBS News tonight. Apparently the commander of the batallion the U.S. soldiers are from decribes it as a "group letter" that the soldiers worked together on, to inform people at home of what it's really like on the front lines.

Interestingly, the parents who say their children didn't write the letters still say they have no problem with the letters, because what was said in the letters is consistent with what the soldiers have said to them, in letters and by telephone.
The parents say the soldiers are too busy to write the story themselves, and their families support the men on the battlefield and the letters sent to newspapers, saying they're glad the facts are being told.

So while the soldiers didn't personally write the letters, there's no contradiction with what the letters report, about what's actually happening in Iraq.

I was actually rather surprised to see a report so supportive of the letters from CBS, which I consider to be a consistently liberal news-source.
I'd expected CBS to rip into conservatives on this, and refreshingly, they showed a public that supports the letters, most significantly the parents themselves of the men in the battlefield.

CBS usually repeats its evening broadcast stories late at night on CBS channels, at least in my area.

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There's also an interesting report on tonight's PBS News Hour, on the dominance of conservatives on radio talk shows, saying (as I certainly believe) that the major television network news and a majority of major newspapers are left of center, and conservatives over the last 10 years have found a counterweight outlet (that previously didn't exist) on A.M. radio shows.
http://www.pbs.org/newshour/bb/media/july-dec03/righttalkradio_10-13.html
[ I updated with a new link, to a written transcript, when it was provided by PBS ]