KDE 4 'consumes 39% less memory than its predecessor'

Not mine, but one Korneliusz Jarzebski (in Polish) has done the numbers (pro-linux coverage in German) and produced a chart showing exactly how the RAM consumption of comparable KDE4 and KDE3 sessions measure up. The result is a mindblowing 39% smaller memory footprint in KDE 4. This just goes to show, that it's worth making large-scale changes to your desktop environment to get the fruit hanging on the higher branches. Wait for the mini- and micro-optimisations to start happening in KDE 4.x, too.