It's supposed to "just work". In an iPhone review (at Ars? One of the big sites.) they tested this, and it worked fine for home use (home users usually do have a firewall...), it only choked, sometimes, on corporate firewalls.
"To use FaceTime on a restricted Wi-Fi network, port forwarding must be enabled for ports 53, 80, 443, 4080, 5223, and 16393-16472 (UDP)"
Regardless, my point was that it would almost certainly not work on a military base. They have gone so far as to ban all camera phones in Iraq, real time video conferencing outside of the military's view is not going to be allowed in combat areas. It also wouldn't look to great over satellite.
At KAF in Afghanistan, a friend of mine was able to sign up for non-firewalled, civilian run, wireless internet access for ~$150/month. It was slow, and used a satellite for uplink. But it was good enough that he could use Skype to have video conversations with his wife.
You do not have to manually forward any ports. Your quote from the Apple KB is taken out of context. Specifically, that article addresses networks with robust firewalls that support policies where automatic port configuration isn't allowed. In these cases, the firewall administrator would have to explicitly allow FaceTime... but this doesn't apply your your average retail purchase router.
FaceTime uses uPnP, which is supported on just about any router you'd buy for under $200 at your local retailer. If you're able to play XBox or PS3 online, your iPhone should connect a FaceTime call without trouble.
You definitely don't need those ports forwarded. If you remember the introduction, Steve listed a lot of protocols. If I remember correctly from looking into some of them, a few were for making connections around firewalls.
Regardless of what Steve said, Apple's official support document notes that you need to have those ports open (or forwarded). I'll go with the documentation, you can go with what Steve said.
That's just stupid. You really think you need to setup a static IP on your phone and then forward ports to it? How would it work if you had multiple phones on the network? It wouldn't. Furthermore, I have several friends that have gotten the phone already, and they were able to FaceTime out of the box in the store and when they got home without any configuration.
Regardless, you can't really argue with the Apple tech note that jonknee linked to - those ports really do need to have port-forwarding enabled for it to work. I'm a big Apple fan, but they still have gotten the firewall-piercing trick down as well as Skype has.
The firewall punching (STUN) works as well as firewall punching works for anyone else. Peer-to-peer between phones won't work if the firewall is setup to block phones, but Skype won't work if the firewall blocks Skype.
A home network and a corporate or military network are much different. Your friends' home network probably has no firewall running on it so all ports are allowed. It's fairly common for corporate networks to whitelist ports and in that case you will need to explicitly open them up or set up forwarding (per Apple's advice).
I'm willing to bet that places like Starbucks and airports who are offering free wifi will start blocking/throttling bandwidth-intensive apps like Facetime as popularity grows. You'll start to see network issues at these hotspots just like you see with AT&T.
It's supposed to "just work". In an iPhone review (at Ars? One of the big sites.) they tested this, and it worked fine for home use (home users usually do have a firewall...), it only choked, sometimes, on corporate firewalls.