Personally, I think the biggest thing Liljegren has going for him right now is stability.
This is a guy who was in and out of the lineup for the last 2 years -- on a very crowded "bottom of the lineup". You have Sandin (who's Dubas 1st pick), Dermott (who's a couple of years older and shown flashes of brilliance), both of whom play a similar style, and then guys like Bogosian, Marincin in there to bring some size.
With Giordano in the picture, and the Leafs substantially more stacked on the left than on the right. Their 3rd pair left shot (Giordano) is now a defenceman that Liljegren compliments, instead of Sandin or Dermott who do much of the same.