Aww the graphics are lovely, I just had to play this=D
I just had a quick first attempt and at 80 metres i'm number one - however briefly that lasts!;-)
I'll leave proper feedback on the AppStore (have Apple fixed the bug that doesn't save feedback left via an iDevice? I'm due you all feedback, sorry!), but here's my thoughts:
The hit area on the help button is too small - I haven't actually been able to trigger the Help button yet. Also, some feedback that the buttons have been pressed would be nice. Maybe the cloud could pop/dissolve into smaller clouds and float away when you touch it?
The game itself is great - I really like the variety of birds - and the flying controls are very smooth. Not to make a direct comparison as that would be unfair, but I found this a lot easier to control than Kayhan's iCopter game.
Unlike that game, however, there's no penalty for flying too high or too low. On the one hand, I really like it as it is as it's less frustrating for players like me who aren't exactly quick to change the orientation of the iDevice, however it would make the game more challenging if say, flying too high created frost on the balloon causing it to crash. I was able to get the (first?) high score just by staying at the bottom of the screen, occasionally having to dodge a bird or two. But as it is, the game gets more challenging anyway as the different birds appear so it may not add anything to the game by changing it.
EDIT: That's what's missing: the balloon doesn't lose height naturally as far as I can see. I've never been in a hot air balloon, but I believe you have to keep firing the burner to gain lift? It's easy to hold the balloon steady as it is. Again, not necessarily 'wrong', it's just something I noticed.
I particularly like how you transition simply into playing the game - I think I should consider a similar approach - and how the progress markers appear on the clouds. I really like the game, the only thing wrong with it is that I can't buy it. I was so ready to part with my cash=D I'll have to wait for your next game;-)