Yes the Peugeots were very fast; they also have 5.5-litre engines but make around 60 kW more than the Audis. They have been on pole position for the last five years straight, and led the race for much of the time each year. However - they have to last 24 hours. In the last five years, Audi have won four times. All of the Peugeots failed this year, while none of the three Audi R15s did - they finished 1-2-3. A good lesson in solid German engineering over pretty French pouffe.
Yes the mighty Porsche 917 has held the all-time distance record since 1971. Le Mans is a race where the winner is the car that travels the greatest distance (the greatest number of laps) in a 24-hour time period. It's not a race like Bathurst, where they try to cover a set number of laps in the shortest possible time.
The big Porsches were outlawed for 1972, and only smaller, less powerful cars were allowed. The Porsche 936, 956 and 962 racers that won the race eight years straight in the '80s were flat sixes, not twelves like the 917. Also, the circuit has been changed a lot since 1971. Today it's longer, and has more chicanes, chases and safety areas than it did in '71. The Mulsanne straight has two separate chases in it today, whereas in 1971 it was a long, long uninterrupted straight from one end to the other. Amazingly, both the 917 in '71, and the Audi last weekend, both completed 397 laps; but now the distance is 75 km greater; an extra 190 metres per lap. See the complete list of winners here:
http://en.wikipedia.org/wiki/List_of_24_Hours_of_Le_Mans_winners
BTW, the winning 917 from 1971, driven by Helmut Marko and Gijs van Lennep, still exists and can be seen today in the Porsche museum in Stuttgart.