Sean_K, depends.
For example, if you have a AP, and are using four APs in repeater mode to extend the range of the original AP. The throughput is reduced, with something like 60-70% in total.
And if you are running all APs on the same channel you will probably have problems to, it will create lots of problems. The AP + Bridge mode is a standard AP mode with some extras with it, but basically it is running in AP mode.
If you are using same SSID and channel for all four APs, you should change it, put them on 1,6,11 or at least with as little overlapping as possible. And use the same SSID name, but with 1,2,3,4 at the end, just to separate them so it is easy to see which AP you are connected to.
http://en.wikipedia.org/wiki/List_of_WLAN_channels