I recently bought the new Airport Extreme Base Station (MIMO 802.11n) to replace the previous dual-band Airport Extreme as I wanted the extra range and speed advertised due to the MIMO antenna configuration. However, I've been having nothing but bother with it and after replacing it this afternoon at the Apple Store, I've discovered this replacement is doing the exact same thing! Basically the problem is that it just won't establish a stable 5GHz network. I've set it up to have a seperate SSID for the 5GHz network for diagnostic purposes and while the 2.4GHz network appears fairly quickly and is very stable, the 5GHz network takes a few minutes just to appear in the list of available networks but I can't connect to it. After a few minutes it disappears from my available network list and reappears at which stage I can connect. However it seems to drop the internet connection after a short while so in essence it's totally unusable for its intended purpose. I went through Applecare, eventually speaking to a guy from level 2 tech support who went through a whole pile of tests etc and determined that it was a faulty unit (either that or firmware issue). He advised I try exchanging the unit for a new one. I did that today and it shows the exact same issues as before. I've found some threads on Apple's support forums and it seems there are other people having the same issue. I'm curious if anyone here on MacRumors has bought the new router and is experiencing the same issues as me? The default configuration is for the 5Ghz network set to 802.11a/n and the 2.4Ghz network set to 802.11b/g/n so even though you might be connecting at 'n' speed you might still be on the 2.4Ghz network. The way to check is to connect to your network and then hold 'alt' before clicking the airport icon at the top of your screen. You will see whether you're connected at 2.4Ghz or 5Ghz. If you're having similar issues I'd love to hear from you. Thanks.