You missed some of the best old iPad uses.
1. My cable provider (Optimum) supports playing all of my cable channels on my iPads, iPhones and Macs so my old original iPad hasturned into a great portable TV for the bedroom, bath, backyard picnic table, wherever. Lay in bed with the Jay Leno Show or Daily Show and wake up to the weather channel, a composite view of your home security cameras, and latest messages and financial updates. It's my favorite portable live video player for all channels.
2. Since it can be left plugged in and always fully charged it's a great go to resource for quick answers from the net and a better composer of quick messages too large to text. Pages, Keynote and other apps let you start something and finish or refine it on a newer device.
3. Add a quick note or make a contact list update and iCloud will let you see it on your other Apple devices. It's handier since it's likely not packed up ready to go.
Your new iPad is likely to be your portable pad of choice but the added convenience of a device with a screen and capabilities that exceed that of your smartphone is great. I would have a difficult time giving it up. My old iPhone 4 is a close second.
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