Well, the reality is that there's no right or wrong answer.. Just what makes sense for you and your environment! I work in a fairly large NetApp-centric environment, and I can say that one of the huge benefits to using NetApp at all are flexvols. They make everything easier, don't they? If performance is secondary to flexibility, I'd possibly say go with NFS. Going down that route, it's a lot easier to add capacity (just grow the flexvol) and it's a lot simpler to maintain overall. With that said, in that configuration for a production environment, I'd plan on having 6 NIC's: 2x for service console/vmkernel (vmotion interface), 2x for vmkernel for NFS connectivity -- yes, I'd keep that seperate from the 'administrative' vmkernel interface, and 2x for vm access. I use NFS datastores on one of our out of use R200's right now and have about 500GB or so of VM's running happily along in a test/dev environment.I will say that you shouldn't sell performance (or iSCSI) short, however. Especially if you're using hardware initiators (I'd recommend it), you will see significant improvement in performance of your VM's, as well as tasks like deploying new VM's, etc.. will seem a lot quicker going across iSCSI. The downside is that you lose some of the flexibility that comes with NFS.
I'd give thought to where you intend your VI to be 18-24 months from now and plan accordingly. As my boss likes to say, take whatever you think it is, double it, and add 20%. You have a unique opportunity now to plan for a to-be state. It never pays in the long run to be short sighted and to only factor in the short term only. Plan as if your decisions WILL come back to haunt you 
