Do a diff between 264 and 266, you'll understand
Basically, Asus archived the source code without cleaning it up first, so you get a bunch of pre-compiled object files and pre-generated Makefiles in there. That will make merging a bit trickier for me as I will need to figure out what to skip and to include.
So far, most code changes seem to be related to Wimax support. They also renamed the option to enable/disable GRO, made the new option default to disabling GRO, and removed the option from the webui.
I also see some code related to IOS devices.
The driver is the same one as in build 260 (same MD5). I have a beta firmware that contains the new driver, the version number is much higher, but it doesn't seem ready yet.