Just to be fair there aare allot of otherdesigns that use screws, orings, and what not to fasten the blocks together. Jaydee #rotor has been makeing them for quite a few years and he uses silicone and screws to fasten his blocks. He even says that he has a hard time getting those appart to clean them. Someone at another forum (don't have the link) stabbed himself trying to get something like this appart.
I have talked to the guys that own dangerden and they said that they have seen the cpu's under pump failure heat up enough to melt the solder off thier blocks. If this can happen with solder I don't think it much matters if you use solder or not. Besides I have seen a picture of what can happen to your block with tap water.
http://www.voidyourwarranty.net/revi...de/index3.php3
Being able to clean this type of stuff out whould be good.