The B-Wing is one of four "Wave 3" expansion sets for the X-Wing miniatures game. I think there are some good reasons to add a few B-Wings to your Rebel fleet; here are those that really stood out the most to me.
First, the base stats for this ship include 3 attack dice, 1 defense dice, 3 hull, and 5 shields (having more shields than hull means they will be less effected by critical hits overall). All B-Wings also have the focus, target-lock, and barrel role actions (note: this is the first Rebel ships with the barrel role action). They can also be upgraded in several ways with a variety of previous and new modifications.
Second, you get 4 pilots (including 2 unique pilots with some very nice special abilities). Pilots include:
(1) Blue Squadron Pilot, a level 2 non-unique pilot that cost 22 points.
(2) Dagger Squadron Pilot, a level 4 non-unique pilot that costs 24 points.
(3) Ibtisam, a level 6 unique pilot that costs 28 points, who has a very handy offensive AND defensive special ability that reads, "When attacking or defending, if you have at least one stress token, you may reroll 1 of your dice."
(4) Ten Numb, a level 8 unique pilot that costs 31 points, whose very nice offensive special ability reads, "When attacking, 1 of your critical hit results cannot be cancelled by defense dice."
Third, it also includes five new upgrade cards (two of which is exclusive to this expansion set at the time it was released): (1) Proton Torpedoes -- a 4 point upgrade that came with several other Rebel ships; (2) Ion Cannon -- a 3 point upgrade also came with the Firespray-31 expansion; (3) Autoblaster -- an amazing 5 point upgrade whose hits cannot be canceled by defense dice (this will likely find just as much or more use on the Firespray-31); (4) Advanced Proton Torpedoes -- another awesome 6 point upgrade that gives you 5 attack dice and allows you to change up to 3 of your blank results to focus results (also comes with the TIE Bomber); and (5) Fire-Control Systems -- a nice 2 point upgrade that allows you to acquire a target lock on a ship AFTER you perform an attack.
As with all expansions, this one includes all tokens, dials, etc. that you need to use this ship in a game (though a copy of the base set is still needed to play).
Given all the nice new things it adds to the Rebel side, I think it is definitely a worthwhile addition to the game. Not to mention that the ship itself looks pretty cool. I liked it so much that I bought 4 of them (I probably won't use more than 1-2 at a time, but I figure better too many than too few).