Re: Pyrex bowl?
the over all feeling i have seen on the bowls that are sold noted as pyrex have been bad. the "glass phunnels" have seemed to have better reviews. i know not that the phunnels are made out of but the pyrex bowls are a borosilica glass (it can take thermal shock better and from a manufacturing stand point the glass hardens up at a higher temp that soda like glass).
over all glass doesnt transfer heat well so you could have part that burns and part of the shisha not hot enough more easily than ceramics. also some have had their bowls break from a very very very small thermal shock when they touched tongs to the glass.
personally i will stick to glass being the base on my hookahs and keep my bowls in the ceramics family