I tried using Sketchbook Express for iPad.

Review:
It lacks many of the more important tools and the ones it has are really... Terrible. It doesn't even have a fill tool and an eyedropper tool, much less a stabilizer. 

Rating: (on a scale of 1 to 10, ten being the best, one being the worst)
2/10
It could be WAY better.

This will probably be forwarded to my art tips book with a more in-depth review. Maybe...

And for now... I'll stick to drawing with ibispaint. It's better then all of the apps I've used.