I flashed in DD-WRT into my WTR54GS router. I followed the instructions step by step. One thing to note is that, the Sercomm utility did not work on my Windows 7 (64bit) laptop. It popped up the following dialog. I had to use a Windows XP machine.
I was under impression it is a v1 router. But Sercomm indicated that it is a v2 hardware that has only 2M flash, 8M RAM. I could only flash in the DD-WRT micro (v24 pre SP2 build 12533). So far, I found that the telnet capability is crippled (does not even have "ls"). Other than that, it seems to be running as expected.
DD-WRT v24 comes with a Repeater feature. It can logon to a wireless network and create another personal WIFI network. That is what I need when traveling with this WTR54GS. I can then connect multiple devices using a single wireless login.
Updates : Firmware updated to DD-WRT v24-sp2 (08/12/10) micro, 14929.