I use the pentax 6mp and as far as water droplets go, I cut out a little square of a synthetic chamois and attached it to the camera cord. Pull into the eddy, bust the camera out of your pocket, ring out the little chamois, wipe and shoot. I found that wiping it with your finger can cause the water to bead up but remain on the lens because of the oils from your finger.
And yes, you have to work on the timing. Autofocus (depress halfway) about 2 or 3 seconds before the shot you want, then it takes the shot pretty quickly from that point. Don't plan on giving your camera to some honky at a waterfall and expect to get a shot with you in it, it definitely takes practice but is capable of great action shots pretty consistently once you figure it out.