1) Never been to Legends, so I can't really answer 1. It seems expensive to me for what it is, which is basically access to a restaurant that's open from 5 to about 10:30 for a 7 PM game. To give you an idea, a hot dog and fries is $14, meatballs are $18, and spaghetti and meatballs is...also $18? (Free spaghetti?) And that's not including the price of the pass. They do have a $55 steak, too...and lots of high end wine that you probably can't get elsewhere in the Garden.
2) All you're paying for is the basically the wristband to get in the door to Legends. Your seat for the game is a completely separate animal - I'm pretty sure that there's no live view of the ice from Legends. (I could be wrong.) I'm also almost positive that the place has fancy TVs to watch the game. And if you do wind up buying a Legends pass, be sure to get one for the correct day, and be sure to also buy a ticket! You can't get into Legends without both a pass AND a ticket to the actual game.
3) "Legends accepts a casual dress code. In effort to maintain a professional environment, all dress code issues are at the discretion of TD Garden and Legends management." I think that means yes - after all, we're not the Tampa Bay Lightning. Seriously, that's a good question - the Tampa Bay Lightning banned opposing jerseys from some of their premium seats during the playoffs, because apparently Tampa Bay is the city where dreams (and old people) die.
Here's video from the Bruins' draft funera...I mean "party"...at Legends, with plenty of jerseys:
http://video.bruins.nhl.com/videocenter/console?catid=662&id=831046&lang=en
But seriously...the Giants? Oh, wait, quick google search - Belfast Giants. That would be MORE than welcome, and I'd be shocked if you had any problems with it. At first I thought you were talking about the New York Giants, a US football team. And, yeah, you could probably wear that too, but that would be both weird and not cool.
4) They take credit cards at the various concession stands all around the Garden. I can't imagine they wouldn't take them there.
Personally, if you want a good experience and are willing to shell out the money, I would recommend buying a Club seat. You get access to the fifth floor of the Garden, which has the Sports Museum - a bunch of old pictures and knick-knacks that are cool, including some original seats from the old Garden. You can grab food cafeteria-style at the west end of the stadium, which might be slightly fancier than the other food in the loge/balcony (although there's a lot of menu overlap). It's your basic American arena food with a few extras - pizza, burgers, chicken fingers, chicken wraps, sandwiches and the like. You're not going to find the $55 Legends steak there. The seats are padded, and ALL club seats have probably the best view of the ice - you're about 16-20 rows back, and your view is completely unobstructed because you're above the glass. Plus, right in the club area is the set for NESN's TV coverage - they're the local network that covers the Bruins. If you want, you can literally get out of your seat during the 17 minute intermission and watch the intermission show live. (And Dale Arnold, one of the presenters, is actually here on HFBoards once in awhile.)
As an example, right now, a loge seat in the center 6 plus a legends pass is going for about $220 total per person on StubHub. You can get a club seat for about $225.
To me, Legends seems like a place where you'd take a business client to get dinner before the game and/or drinks after the game...but I could be totally wrong. If I were there, I'd immediately gravitate to the original yellow Boston Garden sign - at least I presume it's the original.
