I have been unable to reach 300mbps on the 2.4GHz as advertised, even when i move my laptop right beside (approx 30cm) the N750. Signal strength does not seem to be the issue as I am connected at 450mbps on the 5GHz band even with lower signal strength (measure by Wi-Fi Diagnostics on OS X 10.7). How do i correct this?
Have you tried resetting the router?
Do you have other devices connected on that band?