Lynx Beta 8 Download - http://uploading.com/files/m8448d28/Lynxb8.exe/ (PM Me if the link is dead)
A video showing a custom map running on the Xbox - http://www.youtube.com/watch?v=3YYzpBY4CfI
Now, on the graphics. dxsupport_xbox.cfg has a few different settings, but messing with them causes weird and not in place textures. Enabling DX8.1 (HL2 normally runs in DX8) doesn't seem to make a difference. Anti Aliasing doesn't seem to work (or maybe it causes weird textures, I don't remember)
Running hl2_xbox.xbe instead of default.xbe skips the cache check (skips all the videos too) and so you can experiment with your own cache edits (like the dxsupport_xbox edit).
You can make your own intro videos by converting WMV to XMV.
Maps work from around 2004/2005. In the video is used a map called 'lobby' (download: http://uploading.com/files/emc5a1b7/lobby.bsp/
) Replacing the map 'credits.bsp' in the folder GameMedia\maps, with for example lobby.bsp and replacing the name to credits.bsp, when you run the chapter Credits, your custom map will run. We need an old version of Hammer (or atleast old compiling files) and we could create our own custom maps. The textures have a purple and black box thingy, maybe using the command 'buildcubemaps' might fix this.
My blog in Lithuanian about modding HL2 for Xbox: http://www.half-life.lt/forumas-t24364.php