Old thread, but I just figured out the answer for myself
I could install and setup pfSense just fine, it got a DHCP IP on the WAN and 192.168.1.1 on the LAN, but I couldn't ping the box, or hit https://192.168.1.1 in a browser!
The key is to configure VirtualBox's host-only networks; not just the network adaptors for the VM, but VBox's configuration for the networks themselves
Go to: VirtualBox -> Preferences -> Network -> Host-only networks
For me vboxnet0 (the one you get by default is configured as)
192.168.0.1
255.255.255.0
DHCP Enabled
I'm pretty sure this means that if you setup the LAN interface on the VM to be a "Host-only Adapter", your host machine gets assigned an IP address of 192.168.0.1 on the virtual network that VBox sets up for you. This means you're on a separate subnet than the LAN interface of pfSense
TL;DR The Fix:
Configure host-only network "vboxnet1" (or any of the other host-only networks if you're already using vboxnet1 for other VMs) with the following:
192.168.1.77 (or whatever IP you want your host to appear as on the network)
255.255.255.0
DHCP Disabled
The make sure that the LAN adapter on your pfSense VM is a "Host-only Adapter" and that it's using "vboxnet1" (or whatever network you configured above)
Reboot/re-install and http://192.168.1.1 should work now
VBox : 5.1.16
pfSense: 2.3.3
MacOS X: 10.12.2