As someone who has followed the career of Jarome Iginla here in Calgary since he first broke into the league, I think I can provide a bit of insight into what Bruins fans can expect from Iggy this coming season.
Jarome Iginla traditionally has had a slow start to the season. On average, the month of October has been one of his least productive months. In the shortened season of 2012-13, this also held true for the month of January. Iggy tends to take at least a month to a month and a half to really find his scoring touch. Once he does, though, he tends to catch fire in a big way, and usually has a month-long hot streak. The month of November tends to be one of Iggy's best months for scoring. Fans will love Iginla during this period, as he will fill the net with great regularity.
As the season enters the mid point, Iggy tends to cool off. He can go into a protracted slump for a month or two in between December and February. There will likely be talk about frustration and lack of chemistry and trouble finding the right centerman for Iggy. This has been the pattern through much of his career. If he does go into an extended slump, I expect to see him shifted to the Bruins' third line.
How long he would stay in such a slump is hard to say. In the past, he has broken out of it in a little as three weeks, and as long as two and a half months. It does seem that as he has gotten older, the hot streaks have become shorter and the slumps longer. Many think he should do better in Boston than he did in Calgary because of the better talent surrounding him, but that didn't seem to be the case for Iginla in Pittsburgh.
When Jarome Iginla first broke into the league, he was the prototypical power forward. He played a style of game much like Milan Lucic; hard-hitting, crash and bang type hockey, and was not afraid to drop the gloves at any time. Not suprising, since both players came out of the rough and tumble atmosphere of the WHL. Much of that changed as Jarome found more success in scoring, and one year in particular he shed a significant amount of weight in the off season, which since he was already quite fit, meant shedding muscle, in order to try and become faster. IMO it didn't make much difference in the speed aspect of his game, but it significantly reduced his level of toughness and physicality.
Jerome will still get his fair share of goals, but his days of being an elite scorer are behind him now. He is at the stage where he needs to adapt his game to his declining skill set. That may mean going back to being the tougher, more physical type player that he was in his youth. I had hoped he would do so while he still was in Calgary, but perhaps because he was the big fish in the small pond for so long in Calgary, it seemed like taking a reduced role for him was too big of a hit to his ego. Perhaps now that he's not the big fish any more, he will be more willing to accept that role more readily in Boston. If so, I think he could still make a significant contribution to the Bruins, even if he has trouble trying to put the puck in the net.
When it comes to the playoffs, again it is a big mystery as to what to expect from Jarome. He was a huge part of Calgary's 2003-04 playoff run, yet at other times has been near invisible in the playoffs (witness last season's playoffs with Pittsburgh). Jarome has always been a streaky player, and a lot will depend on whether he is on a hot streak, or mired in a slump when the playoffs start. If he's hot, he can get really hot in the playoffs. If he's cold, it might seem to Bruins fans that he's not able to do anything right.