I must say I've had a silent spirit for some 9 months already. I find to to be excellent because I bent out the heatpipes so I can run with a fanless CPU heatsink. I basically copied the SPCR article single moving part PC
. I have an athlon x2 65w undervolted inside an antec solo. With a very slow moving 120mm case fan it performs great. Most of the time the heatsink doesn't really feel any hotter than ambient. Under load (full speed but undervolted a bit) it gets warm but nowhere near hot. Probably in the 40 something degree range for CPU temps. As for noise, the PC is on the verge of inaudible. The loudest part is a samsung eco green f2 500GB (quietest hard disk reviewed by SPCR?) mounted inside a scythe quiet drive. That's mainly during seeks and it's not noise from vibration.
Anyway, I would recommend the silent spirit just because it enables you to do that. I've been very pleased with it and the main reason I went for it was because there was a limited choice of suitable heatsinks. I thought the stock fan was pretty disappointing though. I replaced it immediately and doubt I will ever use it again.
Oh and my silent spirit came with 1366 mounting clips in a little box. LGA1156 clips are available in theory, but the are nowhere to be found it seems. Plus on price, the silent spirit is cheaper at least over here. Around Â£18 (26 USD) compared to Â£25 (36 USD) for the ZZ which is 39% higher.