Using KDE4 on this box, runs nice and quick, it's also pretty reasonable on mem usage all things considered.
Last pid: 3002; load averages: 0.01, 0.10, 0.14
134 processes: 1 running, 133 sleeping
CPU 0: 0.0% user, 0.0% nice, 1.5% system, 0.0% interrupt, 98.5% idle
CPU 1: 3.4% user...