I considered the S class before getting the 450h, but was put off by the reliability reports, so didn't test drive one. I can say I'm glad I didn't get one.
The lag between pressing the accelarator hard and anything happening is huge. Like a turbo lag or the computer thinking about which gear would be most appropriate.
Then there's the constant rumble from the diesel engine.
On the up side, the seats are comfortable, not a single squeek from the trim and a more solid feel to the car. The suspension soaks up the bumps very well, but maybe a little too soft.
Anyway there is no way I'd swap the 450h for one.