we are building our wireless backbone at the moment...
This consists of point to point links between 4 sites around Dunedin (more soon) then clients can connect to omni's (on another AP) at each site. We are using DLink 900 units or Linksys WAP11 in some situations, 24db Parabolic Dish's facing each other.
Much better way as we can stick a router at each main site too to assist with traffic shaping to make better use of available bandwidth.
cost wise, it does mean investing a little more in each site but its worth it.

Cheers
Dan