ASUS RT-N56U
Initial Test On Custom Firmware For UniFi
Thanks to ASUS Taiwan Engineer Cherry for the quick initial custom firmware for UniFi (vlan.500 for internet only) on this device just within a day on 13Jun'11, the fastest I've ever seen from manufacturer ! 
Here are some quick test result.....
This device uses eth3 interface
SpeedTest & PingTest all good !
After running the above SpeeTest & PingTest, surprise to notice this device can auto detect & measure the uplink speed accurately !
Wireless tests, notice the 2.4GHz radio on RT3092 chip, the actual transfer rate seem to improve compare to RT-N13U-B1 (RT3052)
I updated my laptop's built-in Intel® WiFi Link 5100 adapter latest driver, noticed the wooping 300Mbps rate @ 5GHz band on RT3662 chip !! 
Obvious increased in actual transfer rate, I believe this is not the maximum rate yet, it might be limited by my PC.
Tested more than an hour internet, xbox360, uTorrent, all seem to work well, can notice loading become faster, no disconnection/re-connection issue on my Huawei HG655a !
24 June 2011 - New custom firmware from version 2.4.1.4m, tested for more than 4 hours on internet, IPTV, uTorrent, USB2 ext HDD, Xbox360, all seem to be working well, no major issue encountered ! 
Further tests on 2Aug'2011.
Based on custom firmware RT-N56U_1.0.1.4o with current standard Utility Download Master.
2.5" USB2 Seagate 640GB (NTFS)
- Plug in the USB2 HDD to the device, ensure the device can detect it properly
- Go to Network, browse & ensure can see the share drive, noticed there are some folders/files auto-created by the device
- Run the Download Master, click "File --> Connect", it may take some time to detect.
Tested again on another 2.5" USB2 Western Digital 250GB (ext3) without any problem.
Tested download 1 good torrent with excellent speed ! 
Test DDNS with free account with www.dyndns.org without any issue.
Setup DDNS account
Log file indicated DDNS update successfully.
Able to ping the hostname
Click HERE for beta custom firmware & setup for UniFi