MPSS definitely aren't soft, they're actually quite hard which makes it more surprising that they offer so much feedback and grip.
Look at it this way: They may cost you an extra 20%, but you'll get 40% more life out of them and that's ignoring any performance benefits. Any way you look at it, that's a great deal, and that's why even people who normally think I'm mad have been converted to these things. How much is a set of decent wheels, £1500? Now add on the cost of the tyres, lets say £800, you're looking at a total spend of £2300. Make those tyres MPSS and it's £2500, which isn't even 10% extra, and when you're spending that kind of money are you even going to notice another couple of hundred quid?
Sure, it's man maths at its finest, but there's also a horrendous amount of sensible logic in there too.