[Coda]

Curveballs aren't THAT hard to get the hang of:

1. Spin your finger in a clockwise circle until the ball reaches full speed.
2. Move your finger to the right side of the screen.
3. Flick the ball up and to the left (more left than up).

You can also mirror things, using a counter-clockwise circle and flicking from the left side. Do whichever is more comfortable for how you hold your phone and your handedness.

To get an Excellent, you have to hit the Pokemon inside the colored circle when it's small (less than around 40% of its maximum size). This is much easier on larger Pokemon. Don't even TRY on Wurmple. I can get Nice curveballs 90% of the time and Great curveballs (less than around 70%) around 50% of the time.

It's totally worth it to try. You get bonuses for curveballs AND for nice/great/excellent throws, plus getting nice/great/excellent improves catch rate.