The Zyxel P312 router is a unit with tremendous flexibility and so far it  has been completely reliable.  Along with this comes possibly the most tedious and difficult to use USER INTERFACE I have seen.   The interface  started out as an (almost for geeks only) Telnet Interface.  Zyxel is now about half way done with a GUI interface that operates by accessing the P-312 via a webpage URL.  Unfortunately,  only about half of the setup can be done with the GUI and so you must resort to the Telnet interface for the other half.  Changes you make in the GUI interface are saved in the GUI interface and if you make a change via the Telnet interface and go back to the GUI,  you will "think" the change has not
been made.  Confusing?  Yes.    Also,  Making changes via the Telnet interface requires that you "press enter" all the way to the bottom of a particular parameter page and when you finish,  you get no indication of successful completion.

Outbound access to the internet is excellent and fast.  The P312 can support either 10/100 mhz Ethernet LAN.  I have experienced no lockups, or failures of any kind in two months of use.  Software stability has been superb.

Inbound access is another story.  While P312 is supposed to support inbound access to telnet,  http,  and lots of other services,  there seem to be some problems.  With MY unit,  I have not been able to:
(1) Make any telnet connection as long as the firewall is activated. While Zyxel tech support tells me that I should be able to set up the firewall to allow telnet access with the firewall active,  many hours on the phone have not provided any firewall setup to accomplish this.
( 2) Telnet connections are supposed to be able to access ANY port and not just port 23.  Even with the firewall disabled,  only telnet access to port 23 is possible.  Zyxel is supposedly working on these problems,  but I have had the unit for about 6 weeks so far and they have not produced a firmware upgrade to address these problems.

Summary:  If you absolutely know what you are doing around firewalls and routers,  have a working knowledge of telnet and command line interfaces,  only want to use the router OUTBOUND and want a SUPER performance firewall to protect you from outside attack, and have plenty of time to "mess around",  this is the router for you.