I recently recieved a coupon for this game, and I had enough extra money in my steam wallet to purchase this game-- so I did.
This 2-D shooter/platformer is a very fun play and, while I was still in the story mode, it engaged me. I quite liked the concept of a thruster pack, and the manoverabillity and controlls were great. As far as the level design goes, I was impressed by what they had, but I also wanted more. If I had to state one flaw with this game it would be that it is too short. Fun, but short. It doesn't have too many levels. This being said, if you are the type of person who finds replay value in increasing the difficulty of a given level-- you may absolutly love this game. Personally, I was impressed with this game and its mechanics, but I also felt like it needed more content. As a game, I would recomend it to you if you have excess money to spend.
Here's just one more thing to think about with this game: it is well-designed. I am a part of a game-creation/game-theory club at my school, and I have tasked myself to find well-designed games like ShovelKnight. This game, while it may be lacking in content, provides a good refference to game design in that the levels and mechanics are well-developed. The ideas in this game are great, even if it is short.
On the whole, I would give this 7/10 for gameplay and enjoyment, and a possible 8.5/10 if you're looking for good ideas and design in a game.