Not necessarily. On the Kindle it takes about that long because it uses greyscale mode, which is slow, and also flashes the screen first to reduce ghosting, which doubles the time.
In 1-bit mono mode you can flip a pixel in ~100ms, which is plenty fast enough for text entry, although scrolling might not be good.
Early LCDs had terrible ghosting (anyone remember trying to play Doom on an early mono LCD and the image instantly turning into incomprehensible hash?), but I can't find any references for actual numbers for the pixel flip time. I'd be interested to know how they compare to eink. Does anyone know?