For all his positives, Ibracadabra (as he is known affectionately to his supporters) seems to suffer from what I call the "Cristiano Ronaldo Effect". A consistent performer day in and day out on the "small" stages of the Serie A and Coppa Italia, Ibra seems to shrink from his responsibilities and disappear on the "big" stages of the UEFA Champions League, and the FIFA World Cup. While Cristiano Ronaldo has arguably shrugged off that underperforming reputation somewhat after scoring a goal and leading his side to a Champions League final victory, Ibrahimovic still has to prove himself under the limelight of international competition.
While it's obvious that Ibra has underperformed in major competitions, his talent is absolutely undeniable. In addition, it is my personal opinion that he has been relied too much upon by his respective club and national teams for their success. When Ibra does not play well, Inter and Sweden often do not play well. This holds true more for Inter than Sweden, but the fact remains that he is the lynchpin for both sides. In a side such as Barcelona, the weight of expectation is perhaps higher, but is also shared by other international superstars such as Leo Messi, Samuel Eto'o, Thierry Henry, Xavi, et al (depending on who remains after Zlatan's prospective transfer). With that weight lifted, Ibra may well be free to perform to the best of his ability on any stage.