New version just posted not too long ago:
https://code.google.com/p/rt-n56u/
As for NAT loopback (
http://en.wikipedia.org/wiki/Network_address_translation#NAT_loopback). It will not slow you down or cause any other issues. It is better to have it enabled for most users, especially for testing:
NAT loopback
Also known as NAT hairpinning or NAT reflection.[6]
NAT loopback is a feature in many consumer routers[7] which allows a user to connect to its own public IP address from inside the LAN-network. This is especially useful when a website (with domain) is hosted at that IP address.
Consider the following network:
Public IP: 203.0.113.1 (this is the IP of the WAN interface on the router)
Internal IP of router: 192.168.1.1
IP of the server: 192.168.1.2
IP of a computer: 192.168.100.1
When a packet is sent to 203.0.113.1 (public IP) by 192.168.100.1 (a computer), the packet would normally be sent to the default gateway (the router). An exception could be made in the computer's routing tables, but by default the default gateway will be used. A router with the NAT-loopback feature will detect that 203.0.113.1 is the address of its WAN interface, and treat the packet as if coming from that interface. It decides based on DNAT (port forwarding) rules where the packet should go. For example, if the data was sent to port 80 and there is a DNAT rule for port 80 to go to 192.168.1.2, it will send the packet there.
If no applicable DNAT rules are available, the router's firewall will drop the packet. An ICMP Destination Unreachable reply is usually not sent. Note that if any DNAT rules were found, address translation is still in effect; the router still rewrites the source IP address in the packet. The computer (192.168.100.1) will send the packet as coming from 192.168.100.1, but just like when a packet was sent to any global IP, the server (192.168.1.2) will receive it as coming from 203.0.113.1. When a reply is made by the server, the same thing happens again. The packet goes to the server's default gateway (the router), which will find the source and destination port in its NAT tables, and know that it originated from 192.168.100.1. This way, two-way communication is possible between hosts inside the LAN network via their public IP address.
NAT loopback is especially useful when a domain is hosted on the server. The domain name will resolve, unless the user is running a custom DNS server and has made an exception, to the public IP. When the router does not have NAT loopback, any connection attempts to that IP are discarded and time out. A workaround is to include the domain name in the hosts file,[8] but all subdomains would have to be included as well, and all devices in the LAN network would need to have the same modifications. Example entries for the hosts file, following the above network setup:
192.168.1.2 example.com
192.168.1.2 subdomain.example.com