Just a quick comparison, after using my Airport Extreme with Draft-N Wifi in the 2.4GHz b/g compatibility mode for some time I realized how much more speed you can get using the N only 5GHz mode, just for comparison:
Using 2.4GHz B/G/N mode: 140MBit
Using 5GHz N only mode: 270MBit
Since I have 2 Wifi routers at home using 1 for B/G and the Airport Extreme for N only really pays of, suddenly copying large files via Wireless makes sense and is useable. Knowing that the addition of the second Wifi Set in the latest Airport Extremes make a lot of sense, especially when sharing Media over Wifi.