Apple Users

I have what was top of the line, 64 gig, when I bought it and in loading one season of 30 Rock in high def, I've used up most of that.

If storage is a concern, you have to either get a more costly Retina edition or a used or refurbished iPad2 with higher capacity, like this:

$499: http://store.apple.com/us/product/FC916LL/A/refurbished-ipad-2-with-wi-fi-64gb-black-2nd-generation

I highly recommend the item above. For $100 more you get 4 times the storage, and I have gotten several refurbished items from the Apple store, no complaints, full warranty.

For additional storage, there are USB drives which can adapt to iPads, though I haven't used them so cannot recommend:

http://www.gottabemobile.com/2013/04/06/i-flashdrive-for-ipad-and-iphone-review-a-usb-drive-for-ios-devices/