I like getting a small sample that I can play as much as I want instead of only getting to play a few hours on a full version (I barely learn how to use it and then it's over ):)
Many iPhone apps are like that.
Take "Zombieville USA" for example. You get the demo version, you read the instructions, learn how to play.
You go to play it, and you finally finish level one.
It asks you to buy it, and it's over.