I have had gcl for a couple years now, because center ice is not available through my cable provider.
I have no trouble streaming the games through my pc, my phone, or android tablet. I also have roku boxes for my tvs. If you watch the app through your phone, data will be chewed up very quickly. I watched it on a wifi connection, so data wasn't an issue for me. They are crystal clear, and in HD for me. Occasionally, my isp hiccups and it may pause for a few moments, but that's rare.
You don't get to see anything during tv commercials, if that matters to you. Nothing really before or after the games either, just the game itself.
I think it's worth it, but there are some odd things I've noticed.
A couple years ago, the Sabres were playing in Buffalo against the Caps. I live in Va, about 65 miles from DC and the game was blacked out for me. I could see if it were in DC, but playing in Buffalo? wtf?
Any game that's on the NHL network are blacked out as well. My cable provider doesn't have NHL network, so I can't watch the games at all then. Why am I paying to be able to watch the games online, if they block them because they are on a channel I cannot get? In cases like that I look for a stream from a link on here.
Overall, I think it's a good deal, and allows me to watch many of the games I could never watch before.