What factors impact WiFi performance ?

Wireless networks' performance is affected by a variety of factors, such as the distance between nodes, walls/obstacles that obstruct direct line-of-sight, and other wireless traffic in the general area (such as the presence of 802.11b devices in the 802.11g network, bluetooth devices, or the presence proprietary non-standard WiFi technologies).

Cordless phones, bluetooth devices, microwaves, and anything that may cause RF interference in the 2.4GHz frequency range can affect the WLAN performance as well.

Reportedly, even CDs/DVDs can reflect radio signals - keep those CD collections away from your wireless router/AP to improve range.