It's running fine here:
3Ghz HT P4
2Gb mem
Ati radeon X1600XT 256mb

Great demo, I especially liked the exploring mode. Perhaps add some things to collect in exploring mode to unlock things to keep it interesting. (edit: lol, I should read more carefully )

I agree with Exciter, although the bee is flying great it would be a nice if it could fly a bit faster. And perhaps add just a little bit more realism to the bee's skin. At the moment it's véry cartoony and the environment is way less cartoony.

About the environment, it's looking awesome, you guys did a great job. Two things about it though. First off, at some points in the level you can see seems between for example rocks and grass polygons as if they aren't welded together. The 'cliff' like part in the middle (on top) of the island has this if you're flying close to it.
Secondly, you should think of a script to stop the camera from moving into the ground or into models. If the bee is close to the ground it would look better if the camera would not look under the ground, but you probably know that this can happen.

So far so good, looking forward to any progress on this,

Cheers