We're at a time in the series where Waid and Kitson are really kicking things up a notch. There are a lot of plot lines bubbling. There are a few mysteries. For old school Legion fans who liked layers and layers of stories, this was starting to feel like home.
As for Supergirl, we are nearing critical mass on a couple of her plotlines.
One I find interesting is that many of the Legionnaires are completely smitten with her. Cosmic Boy thinks he has a crush on her but it is explained away. Ultra Boy may have a crush on her but it turns out he feels threatened by her power level. And here we see Invisible Kid has something of a creepy shrine for her.
The addition of Supergirl has been a bit unsettling for the Legion. And things are only going to get nuttier.