So... I now have a few OSes up and spinning on ESXi. While I came from a complete windows setup... we got all our DATA disks formatted in NTFS (all the OSes are on VMFS). I can access these through RDM but someone suggested to toss them into VMFses and VMDKs instead. What is your $0.02? Why do you do that?

Yeah.
The main reason would be to take advantage of all the things you can do under VMware with a VMFS file system. A simple example is taking a VMware snapshot of a guest with all of its disks. If your OS is VMfs tools and your data is an RDM, you can only snap the OS.