True for Kraken (although their USD withdrawal policies are very restrictive, so not a huge improvement over getting your money from Bitfinex).

Bittrex has a public pair between Tether and "True USD" [1], but their fiat USD market is not yet available to the public, and I don't know where we can find pricing data for the non-public market.

[1] https://bittrex.com/Market/Index?MarketName=USDT-TUSD