ZDNet's Adrian Kingsley-Hughes compared Windows 7 build 6956 - a pre-beta build, still - to Widows Vista RTM, Vista SP1, and Windows XP SP3 (XP was added in a 2nd post). First of all, he looked at a simple, real world-test: boot times. The Windows 7 build booted in 20 seconds, compared to Vista RTM/SP1 that's respectively 27 and 31 seconds. Windows XP SP3 does it in 23 seconds.
He then proceeded to do a PassMark PerformanceTest 6 benchmark, which again came out in favour of Windows 7 (higher is better): Vista RTM/SP1 1001.3/986.6, compared to Windows 7's 1007.5. Windows XP SP3 did 992. Again, Windows 7 leads the pack.
The next benchmark was PCMark Vantage. "A PCMark score is a measure of your computer's performance across a variety of common tasks such as viewing and editing photos, video, music and other media, gaming, communications, productivity and security." Higher is again better, so Windows 7 beats everyone again: Windows 7 did 5233, Vista RTM 4807, and Vista SP1 4762. For some mysterious reason, the special post which adds figures for Windows XP SP3 didn't include PCMark Vantage.
Cinebench is where Windows 7 seems to trip, and the victory here goes to Vista RTM.
While these results are of course anything but conclusive, they are promising. Windows 7 outperforms its predecessors in most of these tests, which might mean that Microsoft will stay true to its word. Windows 7 is still in pre-beta, so it's very likely that performance will only get better as release time nears.
However, until the guys and girls at AnandTech or Tom's Hardware get a'testin', I won't be saying anything conclusive.