It is possible that Linux does not reinitialize the wireless chipset in the right way, leading to a performance loss after hibernation. Quite a common bug in that area.
The level of detail in this bug report is a little low...
Ask me here or on the Arch bug page (preferred as I will be notified) and I shall provide all details you might need. For starters, I have BCM4311 card and use broadcom-wl driver, i.e. the open source driver released by Broadcom.