Everything you'd expect from a present-generation router is here: PPPoE support; static or dynamic WAN IP; except the ability to enter domain name info for the LAN DHCP server. The ability to change the WAN MAC address is on a hidden page at http://192.168.1.1/mac.htm, but it's there.
You can password protect access to the P1's admin screens, but the router comes with no password by default.
The Status screen shows the LAN and WAN port settings, and has a Reconnect button in case your WAN connection drops. I didn't' see any way to reboot the router from the Admin interface, nor is there the ability to remote manage it (although remote management will be added via a forthcoming firmware update).
You can enable/disable and set the start and end IPs that it hands out. You can also change the address of the P1 and its subnet mask.
The P1 supports 10 single port maps (Virtual Servers), and triggered port range maps (Special Applications). The Special Apps let you specify TCP or UDP ports. You can place one computer at a time in DMZ (outside the router's firewall).
The Virtual Servers ports' are set to 10 commonly used applications and you can't change them. The apps are: DNS, Finger, FTP, Gopher, SMTP, POP3, News, Telnet, Web (HTTP), Whois.
Can define up to 4 groups of IP addresses and either allow all Internet access, deny all Internet access or block access for up to 10 single TCP and 10 single UDP ports for each group.
You can disable the NAT features of the router and just use the P1 as a LAN to LAN router. The ability to define up to 20 static routes will come in handy if you go this way.
There's no ability to save the P1's loaded firmware or configuration. You can't upgrade firmware via your web browser and will have to rely on the Windows based upgrade utility that Linksys provides.
This upgrade utility is different from the one used for the other Linksys routers and it's not clear that a regular TFTP client will work instead. So if you don't have a Windows machine on your network, you won't be able to upgrade the firmware.