We went round and round on this over 6 months ago. This new thread, I think, gives you a pretty good "real life" direction to go. Drive normal, you won't hurt anything if you zip it up here or there, just don't make it a habit. DRIVE NORMAL, and you'll be fine. And in my opinion, 2,000 miles isn't some "magical moment", right after which you can do whatever you want, but right before you would be doomed if you exceeded 4,200... Just think about it, with common sense. As you pass 1,000 miles and approach 2,000 miles, you can slowly enjoy your car more and more.
Myself and others received all sorts of s*** from break-in religious fanatics ("if the manual says this, you MUST FOLLOW PORSCHE'S EDICT TO THE LETTER, HEIL PORSCHE....." as they goose-step back and forth in front of their computers, you get the picture...) because I was so laid back in my approach with my own car.
Ironically, in 6,000 miles, I've still yet to have the need to add any oil to my 997S. It's only gone down one notch on the scale since new. Now, that's admittedly not a conclusive test for future engine longevity and performance, but it tells you something...
I think Fanch is on the money, and his point about the rather arbitrary 4200 rpms illuminates the fact that this is a SUGGESTED GUIDELINE, not an absolute warranty-risking requirement, and it's designed in such a way to keep it simple for the real mechanical dummies amongst us that own Porsches. If Porsche wrote a 2 page thesis on break-in, that covered varying loads, metallurgy, tolerances, and being o.k. to blip up to redline, but don't keep it there, etc.etc.etc..., 1. Most bone-head non-car-guys wouldn't bother reading it because it was too long-winded and technical, and 2. If they did, it would go right over their heads.
So Porsche comes up with a simple bozo-proof suggestion for mass consumption. It protects their interests as best it can, as not all Porsche buyers are ex-F1-engine builders. If Jessica Simpson buys a 2006 997S, she just needs to know "keep it under the numbers 4200 on this gauge, sweetie, until the numbers 2000.00 come up over here...". That, essentially, is why the break-in suggestion exists in such basic and overkill terms. It's the "KISS" principle, Keep It Simple Stupid.
