Today's the day the iPad Air goes on sale, and I came very close to clicking the Buy button this morning on Apple's site. I'll likely go for it, especially once I've had a chance to see one. If you're interested in the 16GB entry-level model, the best deal is at Walmart, where you can get a discount of $20, making the price $479. Plus, 9To5Mac is reporting that Best Buy, Staples, and Apple will all match this price reduction. The Best Buy and Apple offer is in-store only so far, whereas Walmart and Staples list the $479 price online.
As usual with price-matching, you'll need to show proof of the lower price when you go into Best Buy or Apple to ask for the $20 discount.
Walmart sweetens the deal by letting you trade in your old iPad. Their Trade-In page will tell you how much they'll give you for it. My iPad 2 is worth $140. That's a bit less then I'd get on eBay, but it may be worth it, since one avoids the hassle and risk of selling online. In order to be eligible for a trade-in, your device needs to be fully functional, not have any screen cracks, housing damage, or liquid damage.
So far, availability of the iPad Air is still strong, with Apple's website showing a delivery date of November 4 for devices ordered today.
If you're interested in getting the model that connects to the cellular data network, NBC News has a great article giving you an overview of the various data plans and which might best suit your needs. It discusses T-Mobile's free data plan that offers 200GB a month, and points out that you can sign up for this plan with any compatible tablet, not just the new iPad Air. AND the article even suggests that you could sign up for both T-Mobile's plan and AT&T's at the same time. You could use the free offering from T-Mobile when you're not planning to use up a lot of data. And then if you go on vacation, you could swap the SIM card and use AT&T's plan offering of 3GB for $30 per month. (Their $30 plan gives you more data than the other carriers.)