Hello all,
I have also encountered the slowing down of the wi-fi Internet (all areas) since upgrading to Lion on my MacBook Pro 2011, however, I have noticed another odd fact--it is only slow when I am in the room that houses the modem and router. I also have an iMac in that room that is directly connected to the units, but (supposedly) runs on the wi-fi signal, and it doesn't seem to have the same issue. Also, the Pro is dual partitioned to run Snow Leopard, and it is also slow when in the room. When I take the Pro downstairs, it is lightning fast on both OSs.
I am going to run some "tests" tonight to see if having the iMac and Pro running at the same time but spaced apart has any effect because this is rarely the case...I usualy run them both in the same room or sleep the iMac while working downstairs.
Yesterday on the Pro it took over an hour and a half to download an update to an app that was 114 MB while I was working on the iMac doing something else...that seems like an awful long time considering the same update on the iMac took less than three minutes.