If you are having trouble getting Ink to charge, please contact our hardware partner Adont https://getsatisfaction.com/adonit
Ink should work like a finger through any app as long as it is powered on. Unless the app directly supports Ink you will not get the benefit of advanced features like Pressure Sensitivity and Palm Rejection.
One more question for anyone who is having charging problems - when Ink is in the charger, do you see the LED flash red quickly, or slowly pulse red? It should slowly pulse red to indicate proper charging.