venomio: Max you can squeeze out of a 2.4Ghz is roughly about 54Mbps. With 5Ghz you don't get the interference that you would get with microwaves, cordless phones, etc. However, the range on 5Ghz is less than on a 2.4Ghz.
If you're right next to a WiFi AP that can do both 2.4Ghz and 5Ghz, you'll see full ethernet-like speeds to the internet on the 5Ghz connection, where you would be bottlenecked on the 2.4Ghz.
Hope that helped!
Thanks, that indeed answers my question - it confirms what I understood, but good to have this confirmed.