In my opinion, this is a steal of a trade. The Blackhawks needed to dump salary before next season, and Barker was the likely victim anyway. In return, they get Johnsson, who is a better defenseman than Barker, and a pending unrestricted free agent, and Leddy, who was a Top 20 pick in last year's entry draft.
Johnsson fits right in the the Hawks. He is a big (though not physical), puck moving defenseman who can play big minutes. That's key, as Duncan Keith and Brent Seabrook have been visibly running out of gas in recent weeks. Combine that with the long Olympic run Team Canada will likely make, and it's a recipe for disaster. The Hawks needed to add a guy who could play big minutes. Johnsson plays an average of 23:46 a night, and is a +3. Barker, on the other hand, only averaged 13:05, and was showing signs of regression this season. This is a very solid move for the Blackhawks.
The trade freeze is now in effect and lasts until 10:59 p.m. on Feb. 28. This is a great first move, and I think there will be more to come.