I was watching at the beginning but dropped off, only to return periodically when they've featured Superman stuff like Master Jailer, red kryptonite, the Fortress and the "For the Man Who Has Everything" story. Sadly, I'm still not convinced. Supergirl herself is likable, but the show isn't a patch on The Flash.
I agree with those who say the show is too fixated on Superman, even though those elements are what get me to come back. If they want me to stick around, they need to make the story about Supergirl, not her unseen cousin. I'm not sure why he was even mentioned after, say, the second episode. It just makes me want to watch a Superman show instead.