Here is the correct answer to my problem: VMWare Workstation 9 does not support iSCSI booting. It requires "PXE chainloading", where PXE loads to a gPXE (or iPXE) image gives VMWare PXE the ability to bootstrap an iSCSI target. Here are some valuable pages I found on the subject, though none show my specific "PXE boot CentOS from Debian iSCSI in VMWare Workstation 9"... guess I may be the one to write that tutorial up!
PXE Booting Ubuntu from an iSCSI drive
http://www.heath-bar.com/blog/?p=184
Setting up PXE chainloading
pxechaining - Etherboot/gPXE Wiki
Using iSCSI On Debian Squeeze (Initiator And Target)
http://www.howtoforge.com/using-iscsi-on-debian-squeeze-initiator-and-target
