I find thinking while in the shower absolutely the best time to think about things!
Do we censor our true, immediate thoughts by doing this? Having a change of heart on something aside (like, after you think it through, you realize it's wrong and you change your opinion on it) do you believe that we censor our immediate thoughts by attempting to refrain from speaking until we've thought about what we want to say? Are our thoughts -- before thinking before we speak them -- our raw personality and opinions, uncensored?
My honest opinion? It'd be rubbish. The sheer hilarity, randomness, annoyance, and simple confusion that comes out of things people say without thinking about them first is what makes conversation worthwhile. It's just so much more flowing and natural if you're not engineering every single sentence before you say it. Imo, if everyone spent time thinking about what they were going to say before they said it, you wouldn't get to know anyone properly.
That and conversation would be much slower because of the thinking time.