I have been using a Zalman cnps 5000 plus for the last week and am very, very impressed !
My goal is low noise and a modest overclock. With the medium speed fan setting I had CPU temps of 40/45C idle/load, total stability and the fan was barely audible with the case closed. This is with CPU running at 1.48Ghz and 1.75v
I have since changed the fan for a Panaflo L1a running on 8 Volts. This makes the fan totaly silent and despite the modest airflow the cpu runs at 44/49C. This is fantastic cooling if LOW/NO NOISE is the priority.
I suspect that with a Delta this heatsink would give excellent cooling but with the usual price in noise.
I look forward to seeing a detailed formal review by a reputable site and expect it would show that this is heatsink equal to the best if combined with a grunty fan. To also be able to achieve silence (with the approprate fan) and still have a stable 1.4/1.5Gig CPU is also amazing.
My next test will be an 80mm L1a ducted onto the Zalman. This should allow slightly higher airflow with equal or lower noise if the voltage is carefully "tweaked".
My 2c worth.