good one!Here is my personal experience with jailbreaking an Apple mobile device and their warranty...
The first device I ever tried to JB was a 1st generation iPod Touch and it was nowhere near as seamless as it is now. Of course it didn't go well and I was almost ready to toss it in the dust bin because I couldn't get it un-stuck. Of course I knew I couldn't call Apple because I had just voided my warranty. But it was a toll-free number and the worst thing they could do was tell me that they couldn't (or wouldn't) help me.
So I call and this woman comes on the line and asks about the nature of my call. I explain what I did and she said, "No problem, I can help you." As you can already imagine, all I had to do was do a hard reset and restore my iPod. Of course she didn't stay on the phone the whole time, but long enough to make sure it was working.
So I asked her, "If my warranty had just been voided, why did she help me?" She said that if she had not helped me, there was a good chance I would have just thrown my iPod away and Apple would have most likely lost a customer, but by helping me restore my iPod, I would remember this experience and remain a (hopefully) loyal Apple customer who would continue to purchase content for my iPod and (hopefully) buy more Apple products in the future.
And that is pretty much why I have an iPad now.
marie, what are you waiting for?! jb now!