If anyone needs help on working around the bug that TripleEmcoder referenced above, here's what I did:
First, I tried the TrueNAS nightlies which apparently doesn't have the fixed EFI image. So what I did was, install TrueNAS, select UEFI when prompted, and when done let it reboot. You'll notice that the VM powers off due to this issue.
I noticed that pFsense 2.5 installed just fine using EFI firmware in VMware, so what I did was, mount the pFsense ISO in VMWare and boot into it. When it loads, select Rescue / Shell.
From the command line, I ran the following commands. In my case, my drive is called da0, but yours might be ada0 or something similar.
#gpart show da0 <-- This will show you your partition table. If you don't know what your drive is called, you can omit 'da0', but if you have tons of drives be prepared...
You'll notice an 'EFI' partition. Usually it's the '1' spot. The following command will re-install the EFI loader, using the working copy from pFsense:
#gpart bootcode -p /boot/boot1.efifat -i1 da0
-i1 references the partition, in my case it was '1'. da0 is my drive. "-p /boot/boot1.efifat" is the new image from the pFsense rescue disk that will get written to your TrueNAS HD.
That's it! I usually issue a 'sync' followed by a 'shutdown -h now', This gives me time to unmount the CD image. Next time the VM reboots it should load straight into TrueNAS using EFI firmware under VMWare. You might want to do this if you're playing around with SR-IOV or have some other requirement, otherwise just stick to regular BIOS..
Hope this helps someone.