"But I'm fairly sure that I could fund it with at least $140k right away -- my wife and I can each put in $14,000 a year without triggering any gift taxes, and you are allowed to put in the first 5 years on day one. So $14,000 each going into this account per year for 5 years, meaning I could put $140k into it on day one. Plus, we could also set up an account for my wife to inherit. That's another $140,000 minimum on day one. Together, $280,000 on day one. Potentially, we could be looking at $600,000 on day one with both accounts combined (not sure about that gift tax situation)."
This is my understanding. You can contribute, as you stated, the first 5 years ($14,000 X 5 each for you and your wife... $140,000 total) all on day one. I believe that anything above that, at that time, will be subject to gift taxes.
Some resources:
http://www.irs.gov/pub/irs-pdf/p970.pdf
http://www.irs.gov/pub/irs-pdf/i709.pdf