Just bought an Airport Extreme Wireless dual-band N router (January 2012). It works very well and having the separate 2.5 and 5 GHz bands is a fantastic feature. Setup was really easy and it essentially worked 'out of the box'. The one issue I had is attaching a USB Western Digital 1 TB HDD to share on the network and use for Time Machine backups from multiple MacBook Pro laptops.
The drive would appear in the Aiport Utility's "Share Hard Drive" tab, but it was listed as zero bytes and wasn't available to actually share out over the network. I formatted it as a single volume to make sure there wasn't an issue with the drive itself (although it should support multiple partitions on a drive), and it mounted to my Mac just fine, but it still would not work with the Airport Extreme.
After reading several posts on these Apple forums I picked up the fact that the only way most people get their hard drives to work is by purchasing a powered USB hub and connecting that between the Extreme and the hard drive. Some hard drives do appear to work plugged directly into the Airport Extreme, but that seems to be more of the exception than the rule.
The reason given is that the USB port on the Airport Extreme was originally designed for printers and is basically underpowered for proper HDD connections. Adding a powered USB hub not only allows USB hard drives to work, but you can connect multiple USB devices (hard drives and printers) to share over the Airport Extreme through the powered hub, so you do get that added feature.
So if you have plans to upgrade to the incredibly fast and efficient Airport Extreme and plan to do your Time Machine Backups wirelessly (which works very well), add a powered USB hub to your purchase to avoid some frustration. I picked up a four-port powered USB hub at Staples for $30.
It's a great purchase otherwise. Four out of five stars in my review.