Yes, 100kg is quite a bit to strip from a car, but it just seems like they could have made it even lighter, removing some of the interior luxeries. It appears to still have carpets, lots of leather trimming, etc etc... I think they should have gone a little Scud' on the interior and made it even more hardcore, a little more stripped out, after all, the people who will purchase this car over the LP640 will most likely be purchasing it for the thrill alone.
i've seen one in person in washington state. it was hot. it was parked though so i didn't get to hear it.
It's naturally aspirated too, which was shown when it was able to beat the supercharged corvette ZR1 on both turns( of course) and also on the straightways. (It was on this UK car review website by the way)