"fluidity" is a made up marketing term (by me) to mean animation.
But I think this animation is important. Bike is a "tool for thought". I think the way that it "feels/animation" is important. Bike's build built from the ground up to support this. Check out the movie or better yet try the download. Typing feels a bit smoother, text slides into place.
And yes it can be turned off. And no it doesn't slow you down, animations are canceled if you type again before they finish.
I don't have a Mac to try this on, but slides into place sounds like what Microsoft does in Outlook and I ended up turning it off.
Maybe it's not the same thing though. In Outlook (and some other Office programs) as you type the text seems to appear a little more slowly and the cursor glides to the right. To me, it always felt laggy and so I turned it off.
