Hi,
there are lots of causes why theses engines can fail. IMSB is only one. My personal POV: there are some people interested in making money by spreading fear.
And as long as you have oil sucked in the IMS you have a kind of lubricated IMSB – just think about it – it rotates.
I have a 2003 S (US = 2004) and i'm very happy with it, because it hasn't the old variocam camshaft mechanism with the green seals and the camshaft rails that desorientate.
Also it has the better designed cylinder heads.
On the downside there are the weaker open deck 3.2 cylinders. But with the right oil, permanent oil changes and slowly warming up the engine i think that is manageable. We'll see when it fails.
Also think about that an IMSB can be installed the wrong way. It was not intended to be changed by factory. So if somebody does it, he needs to know what he is doing and i'm pretty shure it is important to use the right tools and methods and be careful to get a durable result. And in general: if you find magnetic parts in the oil it's too late for just doing an IMSB. Maybe it's a good idea to install a new IMSB with every new clutch.
Don't see why i should only drive at 2.500 rpm and above.
And if the engine fails it fails. That's life.
Also agree what Gelbster said. The expensive part is the proper maintenance of the car. Even if you don't buy every replacement part at the Porsche d(st)ealership – which you have to do sometimes and if you do repairs yourself.
BTW: we've had a lot of 2.7 FL engine failed, but no 3.2 FL in the last months in the german Porsche forum. Fingers crossed.
Regards, Markus