Slate:

[There are] two main approaches to this uniquely venerable beverage. The austere former — its liquor merely sweetened and seasoned, not even tarted up with a citrus twist — is hard-core originalist. The fancy latter points to the opposite extreme, where the bartender muddles a whole Carmen Miranda headdress and the squirt of carbonated water becomes a long spritz of Sprite.

Personally, I prefer the version served at Rye (which is definitely in the originalist camp).

[via DF]