Compared to last year's, it's faster, more reliable, and just a better car, by a huge margin. As for what needs to be done, it's really nothing we can say without the full information, and some slightly better knowledge of racecar mechanics. The Peugeot and Dome are the class of the field at the moment in terms of aerodynamics - the Dome, underpowered with the petrol Judd, managed to equal the Audi's trap-speeds and corner speeds, though the Peugeot beat them both - but who knows if by how much the aerodynamic performance will be compromised by enlarging the radiators or whatever is needed to keep the car cooled? The 908 might need to compromise some of it's superior pace in favour of a softer drive in rainy conditions, or in favour of cooling and access. Perhaps they also need to redesign the construction of the car itself into a more modular build - the Audi team gains a lot of time by simply being able to replace huge parts of the car at once, as a complete structure. But other than telling them "make it go faster and more reliable", we can't know what's there to change - it's far too complicated for us forum shmoes without big models and hard data.