Each car is allowed two separate energy recovery systems, as long as their energy output and storage capacity can be measured exactly. LMP1 cars will be classed on how much energy they can store, factory teams are forced to run hybrid cars, privateers aren't allowed for the moment (I believe until the hybrid systems decrease in cost enough to be cost-viable for private teams).
Wet tires on a wet-then-drying track is not a recipe for speed. And one stat for you: the fastest car in a straight line all week at Le Mans wasn't the Audi R18, nor was it the Toyota TS030, it was the Sauber-Mercedes C9 that ran in the Group C race. Neither of the LMP1 cars cracked 335 kph, the Sauber peaked at 342.