Stacks Pro for the iPhone/iTouch

Pros: 

Clean interface
Comes with a plethora of decks covering a myriad of topics
Card creationg via web app works seamlessly

Cons:

For best results, one sentence content limitation for either side of the "card"
Substantial screen real estate ends up unused to accommodate word limitation
No sounds embedded or "iPod Accessible" to enable background music to play while studying
Cannot make edits to content within the app
Can't delete bundled decks (most of which are not needed for my line of work)