My philosophy, probably nothing earth-shattering.
Everyone pays within 10% of retail price for apple products (not counting used, or dubious source). Everyone gets ripped off the same amount and there is comfort in that. Further, Apple doesn't drop prices by 50% in 6 months like Dell does. Prices only go down once a new model is coming out, and you can pretty much tell when that's going to happen by reading around. By the time Apple updates, typically 9-12 months from now, you're not upset if they do update. So knowing that the ipad will still be $499 6 months from now, you might as well buy it now. Saving an extra $50 6 months from now (for a refurb model or something like that) is not a big enough incentive for me to wait. It is for alot of people, but not me. Then when os 4.0 comes out, it'll be like getting additional features b/c I will know what it was like to go without them. The iPad is hardly unusable right now as is. Further, the monetary difference between 16 gb and 64 gb is not a big deal to most people. Why? If you can come up with $500, you surely can come up with $700. It's coming up with the first $500 that's the hard part. The extra $200 may hurt up front, but in six months, I doubt most people will be feeling that $200 anymore.
That's just how I operate.