Saw this earlier, and I won't say it blew me away, but I definitely liked it way more than Superman. It really helps that I actually like Milly/Kara's character, and the film wasn't as painfully fluffy as Superman was either.
Positives - Kara/Milly is very likeable. Lobo/Momoa is awesome. The Krypton history segments are interesting. It's a lot like GOTG. It's actually a well made film, with no dodgy filming techniques or cgi.
Negatives - It's so much like GOTG (just without the fire group chemistry) that it isn't particularly interesting. The plot is pretty generic. It isn't so much that the villain is "bad", but there just isn't much relevance or connection to supergirl to make him/them remotely menacing.