As a relative newbie to the wonderful world of SM seating, here are my thoughts after my first season:-
I don't think I drive the boat any harder than I did pre SM
The seats themselves are harder than conventional upholstered seating. I suspect that this is so forces are transmitted to the SM mechanism to force the mechanics to do their job. On a relatively calm passage, my 4rse is numb after a couple of hours, I have to stand to get the blood back into my bootox.
The upper body support is fantastic & you feel as though you are part of the boat.
When it gets lumpy, the seats really come into their own. It isn't until you stand behind them in rough conditions & watch the mechanism doing its job, that you realise how much you are being protected from a battering.
Lateral protection exists, but is minimal, so if you land heavily on one side or the other, you will still get some quite severe lateral forces applied to your spine.
After a day on the water, my knees no longer throb & burn.
The day AFTER a day on the water, I no longer feel like I've done a round with Tyson. No neck/back/hip pain.
To summarise, hard on the bum (& pocket), heaven to the bones. They don't make you invincible & you still have to drive with care especially when it's really rough.
Do I think they are worth the cost? Difficult to quantify, when you look at what you actually get in materials, you think "where's all the money gone into that?" Having used them, I wouldn't want to go back, certainly as I ain't getting any younger.
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5