I've had one on long-term test since November. I have to say, I really love it.
Apart from the sheer practicality of it, it drives superbly for an MPV.
But, for the love of all that's holy, buy a diesel. I've got the 2.5-litre engine that's also in the Focus ST - and it's very thirsty. The 2.0-litre diesel is really torquey, so you've always got plenty of pulling power at your disposal.
And choose your trim level and options carefully: there are plenty of them, but, as with many new cars, they can ramp up the cost.
That said, if anyone asks me what the best MPV on the market is at the moment, the S-Max is always my answer.