Go big or regret it later!
64gb is the sweet spot! The extra cash is worth it if these reasons apply to you.
Four Reasons...
1.) Free Wifi: It's everywhere, so unless you need to be online while on the bus or in a taxi, you can probably wait until you get to work/hotel/coffeeshop. Besides, if you really NEED to check your mail or browse the web for something asap, use your Phone.
2.) Apps: Believe it or not, the biggest space hog on MY iPad's 64 GB hard drive is apps. For example, my favorite app, "The Periodic table of elements" is 2GBs alone. And my trusty "American Heritage Dictonary" is 508 MBs. Don't even get me started on games!
3.) Photos: And not just the photos you'll be taking using the iPad camera, but every photo you've ever scanned into your computer. Imagine your wallet and how many pics you'd stuff it with if you could? Who doesn't want photos of your dog as a puppy to show every random strangers on a big 10 inch screen?
4.) Video: And I don't mean purchased TV and movies. I'm talking about how the iPad 2 (and iPhone) work surprisingly well as video cameras. And the last thing you want is to run out of space in the middle of your kid's b-day party.
Of course you can (and should) sync and transfer all this stuff onto your computer as often as possible. But trust me - you'll always have a few favorite apps, pictures, and video that you'll never want to NOT have with you. And that number will only grow over time.
Many more opinions:
http://www.amazon.com/gp/product/B00746UJBS