As part of my vSphere 4.0 upgrade planning, I checked VMware's HCL for all of my hardware. I noticed that VMware's SAN HCL for vSphere 4 includes the Celerra NS350 for NAS but there's no listing for iSCSI unlike many other Celerra models that explicitly state "iSCSI" and "NAS".
Good News: I opened and SR with EMC support who verified that the Celerra NS350 is indeed supported as an iSCSI target for vSphere 4 just as it is for VI 3.5.
For future reference, one can verify this by using the e-Lab Navigator tool found on EMC PowerLink.