The Calgary Flames found out that bringing a player from a weak/expansion team to a playoff team doesn't mean the stats transfer or improve because of playing on a better team.. There is some buyer beware here.
Leafs finished 2nd in goals for but 18th in goals against ... So I see Leafs adding Jarnkrok to address the later and being brought in to bring the goals against down as priority #1.
Jarnkrok is a pretty average player overall that puts up 12-15 goals and 30ish points.
Also Kerfoot, Engvall, Bunting and Kampf are all UFAs next summer, Leafs are going to need to rebuild their bottom 6 soon and Jarnkork will be a part of that going forward.