OK I use a Logitech M510 wireless mouse...and Logitech dropped the ball on getting things upgraded for El Capitan. I upgraded to El Capitan from Mavericks and everything has been great except my mouse. Now I've posted on Logitech's support forum...they're advice is to pull the receiver unit and reinsert and/or restart...and neither worked..and I'm not the only one. So in spite of all the ball bustin' I've done I'm getting nowhere. I love the extra buttons on my M510...worked great on Mavericks...I use the side buttons for FWD/BACK on web pages... Anyone using anything that works? I'll even break down and get a "Magic Mouse" if it will customize in the manner I'm looking for. Thanks!