This is a goldmine for pre-release and beta firmwares. However, proceed with caution—read user feedback threads for at least 10 pages to see if the "new" version is stable.
Even with careful preparation, things can sometimes go awry. Here are some common issues and solutions: ac8257 firmware new
Not for end-users, but if you are a vendor, you can request the latest SDK and base firmware directly from MediaTek. This is a goldmine for pre-release and beta firmwares