As I understand it, nobody but Nissan ha managed to get The GT-R within about 15 seconds of the 911 Nissan claim it beats round the ring?
And I've heard it can do [surprisingly small number] launch control starts before warranty void/no more launch control/new gearbox/something?
It's getting a bit late now to dig up links, I can do that tomorrow if you want, but the GT-R had one aim in mind and that was to be faster than the 997TT. I think there are enough verified sources at this point to confirm it. DR had the GT-R within 6 seconds around the 'Ring (on the less grippy Bridgestones) against a GT2. And that was a even flawed although you have to applaud their try.
I can't stress enough it is nothing to do with what is the better car, both have excellent attributes by all accounts.
But the basic GT-R has been lifted up to test against focussed GT2's, GT3's, ZR-1's etc. A compliment after initial press testing. I don't think you will find many claiming the 997TT is faster anymore. Auto Sport have just released their results for short track testing and the GT-R was faster than the 911TT.
There is a huge amount of tests and from a few continents and the GT-R fares well or better directly compared to the 997TT, it's intended target. Can dig out links for you if needed.
As far as the LC issue, it became pretty clear that only those who abused it heavily, or opted to boost up are having issues.
If you are really interested, I can follow this up tomorrow or have a look at my previous posts regarding the GT-R.
The problem with (or one of them) is that the GT-R has some basic rumours surrounding a very-well PR'ed car and there is a lot of misinformation out there. Obviously I am gathering as much info as possible, so if I can help, let me know.