Hard or soft...
Well... maybe violent not the right word, but hard.
Hard or soft, the truth or a lie, only you will know. That's what I mean by the uke-nage relationship, it's about honesty. After a while, you will be able to tell which is fake and which is real.
Oh... concerning shihonage, these are a few common mistakes that I've did over the years:
Prob.: Uke's hand is to heavy to move
Sol. : Keep your center, do not let your hand stretch (reach) out.
Prob.: Uke just twirl around with nage (like dancing)
Sol. : Do not let the hand reach up high, keep the hands centered in front of you. don't let the uke's hand higher than his shoulder. Lower your posture but don't bend down.
Prob.: Uke let go off nage.
Sol. : The nage must not force his way through, this causes the uke to sense danger and let go.
Prob.: Nage fall down when turning around.
Sol. : Over-bending of the body that makes the nage off centered.
Prob.: Uke is really stable.
Sol. : There was no kuzushii (off-balancing) in doing the technique. Find the uke's kuzushii point.
Prob.: After the nage has fully turned around, the uke is still stable.
Sol. : The uke was able to regain his balance. Pulling the arm down does not help. Move uke's fingers/hands/arm in a spiralling motion towards his shoulder.
I don't think I've explained it properly here, it's best if it was done visually. But the point above is one has to unify mind and body. Don't let one part of the body move independently of the other, move as one unit.
Be patient... it takes time...