I've got a Linksys Wireless-N home network (WRT300N router & WPC300N adapter).
My router is in the living room and the laptop is 25ft away in the bedroom. Neither unit gets moved yet internal LAN speeds vary tremendously within a matter of minutes. For example, using IPERF, I got these test results from readings taken 5 minutes apart:
[1868] local 192.168.1.101 port 1443 connected with 192.168.1.102 port 5001 [ ID] Interval Transfer Bandwidth [1868] 0.0-10.0 sec 32.1 MBytes 26.9 Mbits/sec ........................................................................................................................... [1868] local 192.168.1.101 port 2461 connected with 192.168.1.100 port 5001 [ ID] Interval Transfer Bandwidth [1868] 0.0-10.0 sec 8.98 MBytes 7.51 Mbits/sec