Sine wave to Digital clock..

I'd say it will probably work as long as the signal on the pin stays within the limits in the device datasheet.

The duty cycle will depend on the actual signal levels and the logic thresholds of the device. If it's a slow/noisy signal you might get multiple transitions as the signal crosses the logic threshold so you'll probably have to debounce the input (debounce methods have been discussed elsewhere on the forums).

Others with more knowledge on the subject might be able to comment on possible increased power dissipation.