I had a look at the new Amel 54 at the Cannes boat show today. I was very impressed - they've fixed nearly everything that was wrong (in my opinion) with the SM.
Waterline length is longer, sail area is bigger. I expect it'll be more spritely in light airs.
The cockpit has been improved with an extendable spray hood that comes out of the windshield. The cockpit table is bigger and stronger.
The stern is much wider with a nice bathing area. The wider stern means it is now possible to fite decent davits - and the yard will do this as an option.
There is much more natural light in the interior thanks to lots of new portholes and hatches. The wood is lighter coloured, and fiddles etc are more modern. It no longer resembles a retirement home for submariners.
The stern cabin is more spacious thanks to the wider stern.
The forecabin is modular and can be either one large cabin, or can be split into two cabins with a folding partition. The washing machine and dryer are in the forepeak.
There is now a huge fridge/freezer where the washing machine used to be in the kitchen.
The nav table is now forward spacing and has a decent armchair. There is now a choice of instruments - buyer can specify Furuno or Raymarine.
It is a much nicer boat all round. The wider stern makes the cabin below considerably bigger.