Well I have a Coolermaster HHC001 which is a copper HSF with 2 small heat pipes built in. It a good sink but I cant say if the pipes do anything. They are supposed to help transfer the heat from the hot base of the sink to the top fins.
What u probaby really mean by "heat pipes" are the CPU cooling systems in the mini PCs by Shuttle and SiS. They have a heat sink of sorts on the CPU and then hollow pipes running up to a second sink that is cooled by the power supply fan. The idea is to save power and reduce noise.
I would guess that a really good conventional HSF supplimented by a really substantial heat pipe system attatched to the HS base and running not to the top of the sink, but to a second sink, would probaby be better than the heat sink alone.
I've read reviews of about 15 or so cooling products that use the heatpipe design, and unfortunately it tends to not work out right. Your better off sticking to companies like thermalright, thermaltake, swiftech and alpha when shopping for a heatsink.