Hi, I have the same issue with my iPod touch (4th gen). Only after I upgraded to iOS 5, did I notice the drop in connectivity with my WiFi.
I have my phone connected to WiFi as wel and it works perfectly. I also have my consoles connected and they do not loose connection.
I sort of figured out a trick which helps when the connection drops. When browsing, I have my settings window open. I have the Wifi settings open which display the wireless network I am on. When my connection drops, I just switch tasks to the wifi settings which I have open in the background and I suddenly get connection again.
This may or may not work, but its just something I figured out with my device. Let me know If it helps though.
I also thought it was my router, but it is not the case.