Competing manufacturers openly use the 911 as a performance reference both in engineering and marketing, and for good reason. Nothing else on the market provides as complete a package of speed, handling, and refinement. The base Carrera, S, and GTS are supremely resolved all-around driving machines; the all-wheel-drive versions will power through any weather condition short of a flood; the 911 Turbos are road-going business jets; the GT3 RS and GT2 RS are as close as any manufacturer gets to selling a racing car with turn signals and a license-plate frame.
Beyond the world-class acceleration and skidpad numbers, the key to the 911's greatness is its civility and accessibility. These are not high-strung machines that require expert hands and are only happy at the limit; an average driver can use – and enjoy – the great majority of any 911's abilities on a regular basis. (Insider note: the new 911 Carrera T, with its lowered suspension and shorter gearing and lighter weight, may be the best pure driver's car of the family in the real world).
What one can call weaknesses in the 911's performance are entirely subjective and rooted in the car's lengthy history – namely, the constant lament that a new 911 isn't as pure or direct as a vintage 911. The current car is bigger and heavier, the electrically-assisted steering lacks the live-wire feel of the old unassisted setup, and throttle response with the turbo motors is inevitably less immediate and linear than the naturally-aspirated powerplants from a few years ago. Such is the price of regulations and shifting customer tastes.