Bought my first iMac a week ago. Since then nothing but problems with wifi connection - intermittent dire slow internet, frequent disconnections etc. I know this seems to be a very common problem but the wierd thing is that apart from the slow connection on the iMac, the Mac itself was trashing the connection on every other device on the network! Seriously - my Lenovo Windows laptop that has worked fine for years just ground to a halt when accessing the internet. I setup a constant ping from the Lenovo PC to google.com and it was consistently either timing out or 3000ms+. Same on my other devices in the house. As soon as I turn the iMac wifi off, everything returns to normal. I called Applecare several times and over the last 5 days I reckon I've spent 20+ hours trying to fix this : Changed wifi channels Turned everything else off (iPad, iPod, iPhone, PCs, printers etc) Changed encryption Turned encryption off altogether Moved router to different part of the house Moved iMac to different desk Removed & recreated locations Refreshed Network settings Deleted System Preferences Bought a new router Tried iMac on a neighbors Wifi connection Checked for interference (there is just three wifi routers in sight of the Mac, mine and two others which are across the street from me) So...... as much as it pains me (because I really like the OS and the product) is that I've just called Apple and told them to come and collect it for a full refund.