[AroundTheBlock_]

That is incorrect. The Mist browser forces you to select a choice upon startup. There was no default. Mist is the most popular client.

[wyager]

And for those who didn't open mist while the vote was taking place?

[zeven7]

Nothing happened for them... Mist is a client that lets you see your balances and send ether or other tokens from one account to another. If you don't open Mist, you don't send any coins on one chain or the other, and nothing happens with your accounts.