About post-mortem, I think I can say the hardest part is to make everything run synchronized in only one thread. In the game itself I am using jBox2D (physics engine) to handle balls movement and brick collision. This engine does not handle variable time steps, you have to guarantee the same amount per second. All the other stuff is easy in comparison
I actually ported my engine from C++ to JAVA in 2 weeks.
BTW: I plan to release the source code for both the game and the engine behind it very soon. (With a good javadoc)
The paddle actually influence the direction and speed of the ball but I think its not perfect, from borders to center the angle modification is from 0 to 30 DEG. If you have a ball going down at 270 DEG and you hit it with a pad border, the bouncing angle will not be that much changed.
About CPU resources, this is true, you can fix this by using Crazynoid_custom executable and enable VSYNC or check CPU-FRIENDLY option. CPU-FRIENDLY option reduce the CPU usage alot but accelerate the gameplay, I am currently working on a better solution.
My game engine handle multiple resolutions based on one resolution, when you start your game project you specify a resolution you will use, for Crazynoid it was 1024x768. Since all coordinates are stored as float, resizing will not break the overall design. The default behavior is to rescale the position and the size of a graphic element but I can also only rescale the position and let the size unchanged. Calculating widescreen aspect ratio is just a question of multiplying a additional value to horizontal coordinate and size. I saw about 0..1 approach from other engines and like you I dont like to have convert mouse coordinates, in my engine this part is handled automatically