They certainly are. I have used many variations with paused deads. Pause below knee, pause above knee, pause below, and above knee, etc. Those who dont believe in static position holds causing core improvement, will be very humbled. They force you to hold a proper position, and fight against rounding of the back. Paused are another one of those exercises that I love. Yes they are brutal, but I think there is a little masochist in every dedicated strength athlete.
Very true. tuchscherer has a good article that touches on paused deadlifts. The pause creates more time under tension among other benefits. I've done paused deads, paused bench, and paused squats. Going to start paused front squats for better core stabilization.