I am considering purchasing a new iPad on eBay and was wondering if there is anything in particular that I need to be cautious about. Furthermore, I am having a difficult time deciding between the various generations of iPads on the market. Of course, I can purchase a first generation iPad for more than half the price as a third generation iPad, but does the difference in performance/technology really rationalize paying more? In addition, I am not sure how much storage I will need. I plan to use it for watching videos, listening to music, and for personal files. eBay suggests 64GB is needed. Finally, there is an option to purchase an "unlocked" iPad. What does this mean, and is one service carrier (AT&T vs. Verizon) better than the other. Thanks for your help.