I don't know how much longevity there is to it but so far so good!
I think that pretty much nails it. I really like it, it's something new and unique, and it's pretty fun. I can't see myself spending much time with it once I've gotten though each level. Two irritations I have so far though are having to slither to move faster, which isn't inherently bad, but moving without doing so is incredibly slow and tedious, and having to sit through the dialogue everytime I try to replay a level is also putting me off going back for collectibles.
Definitely fun though, probably best bought when it's slightly discounted.