Has everyone read Peter King's article?
If they make the trade they probably miss DT Justin Harrell, but could grab RB Brandon Jackson at the beginning of the 3rd round and S Aaron Rouse at the beginning of the 4th round. They lose out on WR James Jones too. At the top of the 2nd round they could have taken Arizona State TE Zach Miller or traded down to get another 3rd round pick to select Jones anyway. Unfortunately when they move down there isn't another tackle like Harrell available.
Generally I hate trading a pick this year for a pick next year. It takes one additional year for that player to show up on your roster. But Cleveland's 1st round pick in 2008 would at least be in the top 10. Dallas got an even better deal than what Cleveland offered the Packers, but Thompson should have accepted the trade.