My production firewall is also an R200 - if you are after an inexpensive rack mount machine for pfSense, I think it's well worth a look.
The built in NICs are Broadcom server grade gigabit parts - they are well supported under FreeBSD, and work with 802.1q VLANs and ALTQ, the system that pfSense uses for traffic shaping.
I think Dell USA are a little 'sharp' in not including the rack mounting rails - they're at extra cost. The sliding rapid rails are particularly good if you have a square hole rack - they fit into the rack without tools, and allow you to slide the server out for maintenance (make sure your rack has the necessary reserve of stability!).
If you have a built in SATA optical drive, you will need to use a pfSense build based on FreeBSD 6.3 (there's a snapshot that is 1.2-RELEASE built on FreeBSD 6.3) or 7.0 (1.2.1-BETA or 1.3-ALPHA-ALPHA), as the ICH9 SATA controller isn't recognised under FreeBSD 6.2.
If you want hardware RAID 1, order the SAS 6/iR controller - Dell's BIOS doesn't support AHCI.
The DRAC 4/P option is rather nice - you can manage the machine via the Ethernet interface in the DRAC card, including powering it up and down, forcing reboot, a remote console (keyboard, mouse and screen via your web browser) and virtual media (you can mount an ISO file or optical drive on your computer as an optical drive on the server). Of course, there's a 'chicken and egg' situation with a DRAC in a firewall - you can't remote manage the server if there's no Internet connection. Still, it has its uses - in my case, the server rack is remote from my desk, but I can manage the servers from my workstation as they all have DRAC cards.