Really nice! Damned hard though 
I guess applets don’t have to suck so badly after all, the user experience (on Windows) was really clean for me except for the security popup. No waiting time with nothing happening on screen, no annoying Java splash screen, it just works.
I have some troubles with the controls. Jumping is so fast, it is hard to use. Getting on top of the house is difficult, the left edge seems easy to hit your head on. Since quickly the enemies land on the ground, most of the effort is spent trying to hit those, which is difficult when jumping is so fast and the terrain is not level. Sometimes I get a cannon with 2 shots, leaving me unable to get to the next ammo box (== dead).