You'd be right that the Visa Infinite is restricted to the wealthier crowd - probably those who incomes exceed $125,000. On top of that, one needs to have generally no less than a 750 FICO, and the Infinite/Black card comes by invitation only. I've not yet seen the Infinite offered by any bank in North America, only high-level Signatures; It's possible that US banks don't care to carry it yet. Internationally, they don't seem to list pricing terms nor annual fees but do mention that your minimum revolving credit access line is at least $20,000 (like the Signature, it's a half-revolving, half-charge card).
If the Infinite offers travel-based rewards (miles, companion tickets, etc.) and no annual fees, then I would tend to think that that card is likely the best one on the planet. However, there is also the matter of the purchase APR...how nice a fixed 5% for the account life would be. 