I live on Long Island as well. I was going to school in MA a few years ago when I first signed up for GCL through NHL.com because i got sick of the bad feeds that were free and illegal (not that cared much about the illegal part). What I'm getting at is, when I came back home from school I kept the subscription. I watch it through Apple TV. Have one in the bedroom and I'm getting the new 1080p one for the living room which has my $5K setup.
Basically, as long as you have cable you're good with the rangers games, so the benefit to GCL is a couple hours after the game you usually can watch the rangers game in full (at least the app on my apple tv allows this) with the rangers broadcast or even the opposing team's broadcast unless it was a nationally televised game which would be nbc or cbc. I also enjoy being able to watch other teams, especially the west coast games in case I get home late from work. Plus during this whole lockout I was able to watch any game from the past season for free (which I'm not sure if NHL.com/GCL usually do that or if they were doing that because of the lockout).
All in all, it's preference. I suggest that you should make sure you have a good wireless router otherwise the connectivity will be slow. Sometimes, but rarely when I;m watching a game or rewind of a game the picture gets blurry while it tries to reload or speed up the connectivity speed so that it is back in HD quality. Also I have iO and their HD quality sucks compared to Fios. The game feeds from apple tv look much better than the cablevision feed imo.
...my two cents LOL