Re: graco my size 70
I have one, and love it. The trick to tightening the harness straps is to buckle the chest clip first, and pull the strap to adjust it BEFORE you buckle the actual buckle. If you try to adjust it after the baby is completely buckled in, it won't really move much, but if you do it before you do the crotch buckle, it moves perfectly. I'm not one to adjust the harness straps every time I put DD in her seat... I adjust them only when they feel too loose or too tight, so it hasn't been a real inconvenience for me.
And to answer OP, it is very well cushioned, DD usually falls to sleep within minutes of being put in it, and she never did that in her Keyfit.