As promised here's my update. I did not get any time to experiment with various vCPU settings, but I can confirm that 3 VM's each with 2 vCPU's seem to be sharing the Xeon E3-1230 CPU (4C/8T) just fine. As far as I can tell the resources are not lopsided, though it's hard to tell. My average CPU usage is only 35% with usage spikes up to 45-50% during busy market hours, so I do have plenty of room to add another VM before those 'spikes' reach into the edge of my comfort zone.
Once I add a 4th VM I'll have a total of 8 vCPU's running on 4 phyiscal cores with 8 logical processors (the hyperthreading) so I assume that ESXi will have no problem distributing the resources evenly anyway.
I thank everyone for their assistance!
Scott