As promised by Apple, and most recently confirmed by Gizmodo via the magic of benchmark testing, the A7 provides twice the performance of the A6 processor.

The A7 is the first use of a 64-bit processor in a smartphone. Based on AnandTech's review, it seems that the bulk of the A7's performance gains do not come from any advantages inherent to a 64-bit architecture, but rather from the switch from the outdated ARMv7 instruction set to the newly-designed ARMv8.

The modern ARMv8 instruction set was designed for a 64-bit architecture. It does away with the legacy support of the last 20 years, which increases efficiency, improving performance without sacrificing battery life.