Unfortunately fails to live up to its promise, but still good.
This series is one of the few that starts of so incredibly strongly that it's hard to believe it could be anything but amazing. Many shows take as much as the entire first season to show just why the characters are likable, create character development, or do anything more than flesh out the universe a little bit. Strike witches has massive character development as early as the first and second episodes, where the main character reveals her heroic character traits but remains completely believable and her power level is as perfectly balanced between "Special" and "Believable" as is, essentially, physically possible for a series of this type.
Add to that an amazing musical score and the presence of flying witches fighting aliens with the equivalent of anti-tank weaponry, and you have a series that really had the potential to be absolutely amazing.
Then, sadly, it doesn't do anything with it. Following the amazing character development and everything of the first two episodes, it degenerates into fanservice interspersed with anti-alien combat. That alone is fairly amazing, but it lacks the great character development promised in the first two episodes. Later in the series(Spoiler alert), there is a plot element that could have been amazing, where the Neuroi apparently try to make friends with our Witches, before being blown out of the sky by ANOTHER set of aliens, but afterwards that event is completely ignored, and again, an opportunity for character development is lost. At the end they try for a heroic sacrifice, but because there hasn't been a trace of character development for nearly a season by that point, it comes off as flat and bland, and what could have been an amazing heroic moment becomes a bittersweet ending. After all, leaving the witches doesn't have to be a bad thing(as being in combat is a tough rap, after all!) but they fall into the easy trap of "It's better to be normal", which is a moral message that I'm really not watching a series about cute animal witches batting aliens to receive.
So my recommendation? Watch the first two episodes. Actually, heck; watch the first three, or maybe even four. But then stop watching, and imagine that they all become great friends, befriend a rogue group of aliens, defeat the alien menace, and live happily ever after. It's what I do, and I'm that much happier for it.