Wow, thanks for the all great feedback, feel very motivated now

Webstart has been updated (no native updates yet - not that I expect you lot would use them

). Details below.
Thanks again, awesome stuff! (coo, how american do I sound these days?)
About the levels that are only available in the purchased version, it's good to load them, but make them unplayable: no mouse-handling, translucent overlay saying the level not available in the demo. This way the player knows that he'll be paying for, now it's one big mystery what the next levels will be, so players will ask themselves whether it's worth it or not.
Done - you can now view purchasable levels - however, most of them arn't designed yet so you'll still get a "duff" noise on these. The nag screen also shows demos of the later levels rolling around.
My second point would be to enable FSAA by default - are you using LWJGL? Use the Display.create(...) to get FSAA - and fall back on the default create() when an exception is thrown. This game desperately needs AA and it's only a few lines of code.
Yep, LWJGL. Unfortunately when I did this I got 3 reports back of a NV bug which causes the windows machine to blue screen when using FSAA and textures under 64x64 in size. Given I've not had many people try it out yet I consider 3 a reasonably signifcant number. Blue screen = too scary to risk.
Last but not least, the register-menu crashes in about a 10th of a second.
The game exits unexpectedly when I click on Register - I see the registration screen for about a second, and then it's gone.
Fixed I think. It was when it was trying to access the clipboard for your license key

"Unavailable in demo" isn't spelled correctly.
Ooops! My english teacher would be appauled.
The rollover areas don't quite correspond to the graphics - noticeable on the main menu and on the + and - buttons in the settings screens.
I've changed this where I notice the problem. Thanks for pointing this out - its a nice detail. For me its key that when you mouse is over the text it highlights, if theres a bit of a border thats ok - just makes its easier to select quickly.
- The view destabilize me a bit : I think It'd be better if it was rotated 45° in the X axis (perspective more visible)
This is the only one I've not done anything about this time. I've been round this loop several times now - trying to make it feel right for more people. The problem with views other than straight down is it makes it hard to see areas when the board is tilted (other parts of the level obscure). I even had the suggestion that I make it 3rd person view - turning it into super monkey ball - its just a different game!
- Nice smooooth loading bar
About the smooth loadingbar.... it seems to be doing nothing the first 75%
Sometimes, you people astound me! You just picked a bug that I really hadn't noticed! You'll now note that start up time is about 5 times faster. Why - I shaln't say - its way to emabarrasing

Wow, this game kicks ass
You said kicks right? not sucks

* Fullscreen mode! :-D
* Keyboard controls. Yeah, I know, that might make it too easy, but right now, I'm fighting the controls, not the game.
You've just topped the kev-o-meter for these requests - had feedback asking before but you've just made the feedback big enough. Both are in:
Keyboard - on by default - Enter/Space to click, cursors to control. Note that if you use a gamepad keyboard and mouse controls are turned off. All menus should as a side effect work through keyboard also.
Fullscreen - theres now an option in display settings for fullscreen (which can also be toggled with F9). Switches into the res of your desktop.
Thanks again for the encouraging feedback, apologies for the long post.
Kev