May not be compatible, AFAIK mixing chips doesn't work well with WDS, and no, WDS is not, nor probably wont be a standard due to that fact alone. To become standardized would mean it would have to work with any chipset configs, and since mixing doesn't work well (i have read VERY few stories of success in dd-wrt with WDS mixing of chips, when asked to show screen shots, the user that makes the claims always seems to magically vanish...hmmm)
I personally have tried mixing and it doesn't work with WDS, now you can set it up as a client mode repeater using dd-wrt.
The netgear you have is a broadcom unit, if you intend on keeping it your main AP, i would suggest another broadcom device to go along with it. The Buffalo you bought is an Atheros unit, so whichever you keep as the main AP i would match chips to follow suite. But remember, as i said, you can still link them, just probably not with WDS.