I have heard this from a Professional Racing driver during one of the recent NNJR PCA meetings (Andrew Davis) that Porsches are quite good even in the rain - I figured out because of all the weight on the rear wheels giving the traction required. He's an instructor at the Racing Schools and also mentioned that PSM won't interfere with your driving unless you just don't know how to.. Its there just to keep you safe when you cross the limits.

 

Every one has their own limit. Porsche sets the limit to the lowest common denominator. This is to protect everyone down to the worst driver.
These limits are too intrusive to people that can drive beyond that limit.

For example I have experienced while cornering going up a hill sideways. I need to get on the brake at the top of the hill to make a sharp corner. I expect that when I brake I will rotate the car to increase my slip angle. During this if the limit is crossed I'll feel the car twitch and it will suddenly cause the car to straighten out at I can not rotate the car like I wanted to. If I keep more lightly on the brake and rotate the car more slowly then PSM won't come on.

If you want to drive sideways, you won't be able to go sideways for very long. This is why GT2/3 cars in later models with PSM have increased limits programed so that it is less intrusive.

 

Unless you hit an unexpected slippery surface, oil, ice, etc.

 

In my '01 if the rear begins to come around, kick out, as long as I am quick enough with the correct level of counter-stear PSM remains inactive. PSM gives the driver "just" enough time to react correctly for an event.

 

I like that I can drive the car to 11/10ths, and PSM will 1-wheel brake and other magic to give 10/10ths worth of performance, and make me look good

I hate like when it retards the throttle, though.