Just finished a few days testing this new device on both my old iPT2GMB. I was having trouble getting the Peel 520 to make calls using iOS 4.2.1. I followed the steps very easy add the 2 cydia sources & the mobile substrate worked fine with iOS4.1. I was working with clean install of iOS then I decided to try different things and on my last attempt with clean install I only added 1 thing extra "Winterboard" and that got it running properly in iOS 4.2.1. Winterboard is not listed as one of the steps to get this working so I have sent the peel 520 team my finding. Most people would probably have "winterboard" installed but like I said I was working with a clean install and only using the direction found on the peel520 website. I have test this device using H20 SIM, AT&T Go SIM and even my iPhone 4 SIM using an adapter all work good with some bugs here and there but overall a neat toy and the prices have dropped. So go grab you one if you got an iPod Touch and want to play around with a new toy. Next up I will test a C Peel once the Novelty price wears off. Hope this info might help those trying to use this device with iOS4.2.1 and hopefully they get the "winterboard" step added to the instruction. Thanks.