https://en.bitcoin.it/wiki/FAQ#Is_Bitcoin_a_Ponzi_scheme.3F As mentioned in the link, Bitcoin certainly has tremendous value beyond simply making early adopters rich. If you don't believe it, I encourage you to listen to some of Andreas Antonopoulos' arguments about Bitcoin as a network vs Bitcoin as a currency. Bitcoin provides a vast number of benefits as a technology beyond simply being a "currency."
He probably made a mistake evoking Ponzi's name (although he never actually called it a Ponzi scheme, which it clearly isn't). But I think when people bring up Ponzi and bitcoins, the idea is closer to a bubble mentality where adopters are buying bitcoins to profit, not to use it as a currency ("bitcoin isn’t means of payment as few transactions in Bitcoin. And given its volatility all who accept it convert it right back into $/€/¥"). This, at the moment, is correct from what I can tell - it's much easier to spend cash than bitcoins on legitimate things. People aren't getting bitcoins for, say, the same reason an American going to France will get Euros.
There may be theoretical technological benefits to crypto-currencies, but they don't practically exist for most people who want to legitimately spend their money today. The only useful application I've seen so far are the microtip dogecoins on reddit.