I use RunKeeper on my iPhone. I love it. I love that it saves all the data to a (runKeeper.com) website, so you have history of every activity and your route.

You should know that RunKeeper recommends that you disable your WiFi and Push notifications before you start your activity. Battery life is greatly enhanced. I have done 2-2 1/2 hr rides without losing my battery.

FYI- the iPhone 4/with the OS4 is supposed to have a shorter battery life than the previous 3G/3GS model. I have a 3G and intentionally have not upgraded to the the new OS because of the battery issue.