I upgraded my black Macbook (4,1) to Lion yesterday and early this morning, noticed my WiFi quit working. I turned off WiFi and went on using ethernet since I always have that connected anyways. I then started seeing posts about this on the Apple forums from the 10.7.3 update.
I haven't upgraded my 2010 MB yet, it's still on 10.7.2. I'll wait to see what happens for while before I upgrade it.