High resolution drawing app for iPad I'm looking for a good app that I and kids at my home can use to draw pictures on the iPad. I've used many of the free apps, like Chalk Pad and so on, but I notice that each of these comes with a lag.

What's a good app which helps you draw great looking pictures and has a minimum amount of time lag? I'd prefer free apps, though mentioning paid apps won't hurt.
My girlfriend uses iDraw for vector picture drawing. It’s not free, but it’s the best iPad drawing app I’ve seen. It also has an OS X version.