Most people who have "cut the cord" from cable or satellite are NOT sports fans. It's great if you can cut the cord and save money, but probably 99% of sports telecasts are on pay TV channels. If you're just a hockey fan, you can still watch through GameCenter, but good luck in the playoffs when the only over-the-air televised games are weekends on NBC and 2 or 3 SCF games.
I've sampled GameCenter, but the quality is nowhere near what you get through Center Ice on DirecTV. Center Ice through Comcast is a complete joke, you're lucky if you get 2 HD games a night. Plus they share channels with MLB Extra Innings.
I'll gladly stick to satellite and SlingBox, which lets me watch anything when I'm not home from my computer, tablet or phone (live TV, DVR, etc).
The quality through gamecenter is HD. I will have to figure out what I will do for the playoffs if the Devils make it. Last year was my first year with out cable and I was fine with the feeds I found or watching games a day later (since the playoff games will be on gamecenter the next day.) But I am not really a big sports fan outside of hockey.