We did a basic eval of NMP since it was included with vSphere (and since PowerPath VE currently requires Enterprise Plus, though I've heard that may change), but went with PowerPathVE in the end.  We're a mid-size org and with the number and frequency of VM-related modifications we perform, NMP would have required much more manual process.  We were actually able to estimate how many more "person-hours" per week NMP would require.  PowerPathVE automated all this for us (though at a cost), but we recouped that almost immediately with having to purchase fewer array engines and HBAs - PowerPath actually allowed us to save HW costs right away.