My issue with Lion was that it broke WiFi on my 2009 iMac. Yet the 2011 iMac is just fine with it. There has been a near constant running thread on the Apple support since the day Lion dropped. All sorts of WiFi just going out, sometimes even with the icon being nice enough to gray out.

Currently at 145 pages and growing https://discussions.apple.com/thread/3191630?start=2160&...

Yeah, the 2009 iMac started working the day I put Snow Leopard back on it. I then sold it and warned the owner that upgrading to Lion was at his own risk. I replaced my router with an Airport Extreme; useful excuse to buy a new toy; at one point to see if that resolved it. I even moved the iMac NEXT to the router one day.