Just back from my first ever trip to New York or USA and I absolutely loved it. I will do a trip report in a bit with full, rambling details but I just wanted to give a quick bit of advice so someone else can avoid my mistake.
People might think this is painfully obvious but it did catch me out.
If you are wanting to have alcoholic drinks while at Madison Square Gardens and you are from outside of the USA (I don't know if Canadians would be ok) make sure you remember to take your passport with you not just a driving license. I get used to using a driving license when travelling within the EU as ID for drinks so didn't think to take a passport but here they would not accept it. They did seem to be asking everybody to show ID, even people who were clearly about 50. This was at an NBA game, I can't vouch for any other events.
Just thought I'd let people know as it did detract from the experience slightly not being able to have a beer while enjoying watching what was otherwise a great game. Well Golden State were great, the Knicks were woeful :) but I enjoyed the experience.
As a side note, getting tickets from Stubhub for collection was really simple. Just note that you don't pick the tickets up from the venue, you get them from their office just off Broadway.