I've not had much experience with it yet-- just the Athlon MPs before the mobo konked out during BIOS re-flashing.
However in that time I found it worked very well. The processors stayed chilled and there was absolutely no residue in the tubes or discolouration of the blocks. The pump had no trouble with it either. It has a very low surface tension so it makes good contact with the blocks and rad.
Some guy on
Wizard Designs Forums has been using it for a while on his dual Xeon system and he, too, swears by it, finding it very efficient at cooling without having to worry about corrosion or algae growth.
Since it is roughly the same price as FluidXP, I think it is worth the expense --especially as a potential leak won't fry your expensive hardware. When it spills, it evaporates harmessly leaving no redisue whatsoever so you wouldn't even need to clean your components.
PS: just a thought... next time just PM me.