Certainly on the Airbus 320 series I don't think you could tell really from the cabin, generally it will perform a 'positive' to 'very positive' touch down. I brace for impact during touchdown on BHX 15 autoland.
I tell the passengers if we are about to carry out an autoland and it is my sector, gives the passengers some background info and saves a red face when saying goodbye to the punters and it has just slammed it in. I have done one 'real' autoland in the last 6 months and the rest in the sim. The real autoland was still a practice in greater than CAT I conditions.
Cheers.