One of the biggest criticisms that Airport Extreme draws it the fact that it uses a Mac or iOS-specific set up the process. Rather than using the traditional web page based approach, Apples employs a different method. It is quite an odd choice since you have to use a Mac or an iOS device to set this thing up in the first place. Although once set up, it has no problems to connect with any operating system whatsoever.
You can manually select channels or let the router decide for you. Also, you can configure the radio and password protect them as well. Although there is a VPN pass through available, there is no VPN server that you can use.
One more nuisance is the fact that there is no option to change the MAC address. Many ISPs lock the internet connection to a particular router or a modem. In that case, it can be a headache to shift on to the Airport extreme if you were using a different router or a modem before. You can still use the Airport Extreme, though, but you have to contact your ISP to update their MAC addresses, and that can take an hour or two. So, although it is not an issue, it is a serious inconvenience. Although, if your ISP does not lock your MAC address, there is no issue at all.