I jailbroke my iPhone before the App Store started up. Then I un-jailbroke it. I just didn't see the need, even though it is really easy.
I tried jailbreaking mine with a laptop in the parking lot before leaving the store. Hung it halfway through, got home (120 miles/2hrs later), then finished jailbreaking on my desktop. At the time I didn't feel it necessary, just wanted to check it out. Now that I use SBSettings, I find it nearly invaluable.
...but people can pirate apps from the App Store?! I thought Apple had it pretty much locked up.
No, they sure don't have it locked up. I wanted to try out the Slingplayer app with my 1st gen Slingbox, but didn't feel like paying $30 for the privilege. A few google searches, a download over Bittorrent, and I had an unlocked Slingbox.app to install on my iPhone. Works a treat, though without 3G in my town, I don't feel it's worth paying $30 for. (Though technically it's not supposed to work over 3G, there's a JB app for that :)