It is an excellent router and gives me some of the best LAN speeds of any router I have used. I use it in conjunction with Airport Express's for AirTunes. Simultaneous dual band is amazing
Edit: Just to Add I am a big fan of Time Machine....however you are able to add any external to the Airport Extreme via the USB port...however it's nice having it built in...
In your setup simultaneous will be clutch, as devices such as the iPhone do not support the 5GHZ band, so your other devices can take advantage of it while you will still be able to get your iPhone hooked up via the 2.4 GHZ band.. (5ghz higher throughput for media streaming and time machine backups etc)