Windows 7 has been receiving high praises as far as performance goes since the operating system debuted into Beta. Not even at the Beta Build 7000 level and not at Release Candidate (RC) Build 7100 was Windows 7 criticized for any sort of performance issues. On the contrary in fact, Windows 7’s new task execution speed, responsiveness, lack of hangs and freezes were applauded across the board by testers and adopters. Just imagine an operating system that is at the opposite pole compared to Windows Vista RTM, which was crucified as soon as it hit the shelves, and found to be slower than its predecessor on the same hardware. In contrast, Windows 7 has been receiving nothing but accolades performance-wise, and well-deserved accolades at that.

Windows 7 vs. Vista SP2 vs. XP SP3 Performance Comparison - On multicore - Softpedia