Shields Up?
Perhaps the first thing you should do with a new router is use Shields Up to check if your router has any open ports?
I haven't used CLI on a router for a long time (used to have a Perl script to tune the ADSL) but I suspect that there is probably a lot more functionality under the hood on most routers than is exposed via the web interface. So access to the CLI (which will probably be Telnet) internally is IMHO a good thing on balance.
Not externally!