I had ample time to buy this but the method was just undesirable for the cost. I don't need to tether my MBP, just my iPad WiFi. I still like my decision of giving up my unlimited data for the 4GB tether.
Not sure why people want it either? 1) it's extremely restricted in use (not even comparable to android tethering), but 2) say good bye to unlimited, AT&T especially can easily tell when your tethering since using a computer to do stuff use much more data online then the iPhone. They can see spikes in data usage and it's an easy excuse for them to pull your unlimited w/o actually proving whether your were tethered or weren't. And if your on one of the normal plans they can force you to pay the extra $ for tethering.