This movie is like a sci-fi Groundhog's Day in many regards. I have been a great fan of the formula. Especially in the 90s, it was sort of required that every TV show has it. Xena, Stargate SG-1, Buffy are some memorable examples. The formula is this: a person gets stuck in a time loop for some reason. The only way he / she can get out of it is by solving why they got into the loop, and changing something about their life. It usually requires learning some new ability as well.
A problem that this formula can have is that it becomes boring after a while. I remember that the Xena episode had this problem, because she was doing the same thing too much. Stargate changed this by putting some funny elements into it, like when O'Neil played golf at the Stargate. What this movie did to keep it from boring was the huge learning curve that Cage (Tom Cruise) went through, and his romance with Rita (Emily Blunt).
The story itself is not boring at all. From the trailer we can gather that it's about an alien invasion. We don't get to see the actual aliens for a while at the beginning, and the anticipation is a real adrenalin rush. The loops were done in an interesting way, and even a bit of humour was put into it. The explanation for the loop didn't seem too far fetched.
In many regards, Cage is a classic Tom Cruise character. He flies a helicopter. He rides a bike. He has a gun. He wears a uniform. He broads in a pub with a drink. He is the hero. Cage does have character development, because while he starts out as a man concentrating on survival, he becomes someone who knows that sacrifice is the most likely outcome for the good of all.
Rita is kick-ass character. I really loved her a lot, and Emily was great at it. I haven't seen her do an action movie before, okay, maybe Looper, but her character was different there. I really thought she stole the show for me.
Overall, a really enjoyable movie. It has some surprises that I didn't see coming, which is pretty unusual. I recommend it not just for sci-fi, but also plain action movie fans. The romance is not too much, barely there actually.