I am really tired in general of fans booing almost every athlete who leaves their city, when they return in another team's uniform. There is the odd guy like a Bourque or someone like that who still received cheers but they are few and far between. Yes you paid your money and you can do what you want but in a lot of cases it makes no sense. Before I get to Seguin I will give my opinion on some others who have left organizations fairly recently.
Parise I would boo because he left New Jersey the first chance he got even after they made him the Captain and they went to the Stanley Cup Final.
Alfredsson should not be booed. He did everything for that organization and if at this stage in his career he wants to go somewhere else nobody should take issue with that.
Nathan Horton you might want to boo him because he left Boston at the first chance he could but he was not a long time Bruin (not drafted by them so you wouldn't necessarily expect him to have a loyalty to the organization). I would prefer to cheer him for the contributions he made in the Stanley Cup run in 2011.
In regards to Tyler I guess you might boo him for not performing to expectations from a scoring point perspective during last year's Cup run. A few more timely goals/points could have meant we were celebrating another Stanley Cup victory. You could possibly boo him for partying too much. In both of these cases I say he is a 21 year old kid and although you get guys who mature quicker - Toews, Crosby - you can't expect all young hockey players to mature at such a young age. Most importantly I would not boo him because he did not ask to leave Boston and even though it was only 1 game I think there is a strong possibility that they don't win the Cup without his big performance in game 2 of the Eastern Conference Final in 2011. He was often fun to watch when he was here. I wish him all the best and I think as he has said as a Stanley Cup Champion with the Bruins he will always have a piece of Boston with him.
As far as whether the trade was a good one or not, that remains to be seen. I think it was a good trade for both teams and Seguin probably did need a change of scenery to get him to realize he needed to change some things. I do think that the player who has the most upside potential by far is Tyler so it could come back to haunt the Bruins but he may not have gotten there if he stayed in Boston. If the Bruins win another Cup in the next few years it won't matter.
The only other thing to note is that so far both Marchand and Bergeron are struggling to put up points. It is early but whether he was scoring a lot or not Seguin garnered a lot of attention from the other team's defense. With his speed he opened up space for Patrice and Brad. I am sure Louie and Bergeron will click once they have a chance to play together more but in the short term they are missing Tyler.
If I had been at the game last night I would have cheered Seguin before the game started. After that I would be cheering for my Bruins and he is simply another opposition player they need to shut down.