I have a wireless network in my home. I'm downloading via bit torrent. On a reliable torrent I see my speed increase gradually up to about my max (roughly 1.5MB/sec), then all of a sudden the traffic spikes down to nothing and crawls back up. This happens about once every 5 seconds.
My wireless network is driven by a Netgear WGR614 v7. I'm using WPA2 encryption. It's in another room, but the signal strength appears as 4 bars in my wireless browser. Also attached to the network is an airport express (as a client, not an extender).