The first benchmarks have come in comparing the iPhone 4S performance to the iPhone 4. 

Online website Anandtech used Geekbench to compare the two devices and found that the iPhone 4S (623) was 68 per cent faster than the iPhone 4 (325). This is below what Apple had been reporting because they said the new iPhone was twice as fast.

Interestingly, the benchmark , which looks solely at processor speeds showed that the iPhone 4S was slower than the iPad 2 even though it contains the same CPU. It can only be assumed that Apple has toned down the speeds of the processor to reduce battery power.

Anandtech also used GLBenchmark to test graphics performance and the iPhone 4S performed 7 times faster than the iPhone 4, which are the figures Apple reported. They also benchmarked the browser which shows huge improvements in speed.

Source