I think the presentation is excellent, it has a very Mario feel about it with the background music and the end animations and so on. The idea is good in that it is basically something a bit different, and from the three levels I've played different mechanics come into play as the game progresses.
The control doesn't seem to quite be intuitive enough, though I'm ancient and that may come with time anyway.One of the problems with writing and testing your own games is you know how to play them and often forget that someone else just picking it up might find it much harder.
One possible bug/issue occurred with the walrus at the start of level 3. If you grab the air bubbles by pushing down but don't quite get the expand and jump thing right, and land down on the Walrus again, then it doesn't seem possible to get any more bubbles by pushing down and you are stuck (obviously you can quit the level) - I'm not sure if it was designed this way
On that, I'd be half inclined to borrow from Miyamoto again - when you get a new mechanic, like the inflation and flying thing (don't know how many others there are ?) Mario games sometimes to have an area where you can just play with that mechanic with no 'threat', this helps a player get a feel of it.
One way round the 'is it worth the money ?' thing - maybe you could provide a limited version with only 3 or 4 different levels at various stages in the game - something like that ? I remember that working spectacularly with Lemmings 30 years ago Or a few levels for free with IAP ? Maybe see how well it sells ?
If I was considering buying it, I'd wonder if the game was basically the same throughout or it had more difficult/challenging levels with extra ideas - powerups, challenges and so on as it got further on. The three pictures suggest to me that you are varying the graphics in the game, not actually changing the game. I think a video would be a great idea, showing the game at various levels - rather than just simply videoing the game you might even consider videoing playing the game, partly, to show how it actually plays.
But I think it's well worth $0.99 and if the game does change and expand as you go on it could well be underpriced. If it has the same mechanics but more difficult challenges (e.g. harder jumps and so on) then it's probably about right.
Good luck anyway