Background info:
  http://wiki.debian.org/brcm80211
  http://wiki.debian.org/wl

User reports concur to indicate that the free brcm80211 / brcmsmac module are
not on par with Broadcom's one, unfortunately.

Installing from unstable for compatibility with newer kernels.

Additionally, the package from unstable automatically blacklists the conflicting
brcm80211 and brcmsmac modules. See Debian bugs #597786, #601009 and #611539 for
details.