Hi,
I've got a D-Link 704P Router/Switch box, a Linksys BEFW11S4 WAP 11+Switch, a D-Link 810+ Wireless Bridge, and a D-Link 900AP+ WAP+Switch in our home wireless network (802.11b). I finally got around to upgrading the firmware tonight.
Previous symptoms:
On a cold start of all of the networking boxes the speed would be wonderful with our cable modem connection (~100+ kB/s FTP). But after a few minutes or certainly by the next day the speed would usually degrade to ~4 kB/s. Software Updates from Apple to our Dual 2 GHz G5 box would usually time out before mult-MB downloads would complete. Several attempts would be required.
On upgrading the firmware in the networking boxes, things seem to be much better. The speed seems to be staying high. Time will tell though.
If you're dissatisfied with your WiFi boxes, try upgrading the firmware if you haven't done so recently. It may help.
Cheers,
Scott.