i transfer a lot of media around my house to 4 computers and usually large files and sometimes i am streaming media to one and want to transfer files and i found N to be worth every cent.
if you are going to be streaming and transferring files or downloading files from the web i HIGHLY recommend it.
after a lot of trial and error i found that having anything G connected to my network severely crippled my transfer speeds so i set up 2 networks as briefly described below.
i also found that even know i had he extreme N router it was an older version and was not a gigabit connection but "fast ethernet" and this was also crippling my transfer rates from my devices hard wired to my router (ie iMac, Network Storage Device) which had gigabit connections but could not get the speeds with the older extreme fast ethernet.
i switched to a an extreme N gigabit router and changed my network cables from CAT5 to CAT6 and this also greatly increased my speeds between machines. standard CAT5 can not handle gigabit speeds so i went with CAT6. i believe you can use something called CAT5+ or something like that but the price is the same so i went with CAT6 to be sure i had the best speeds.
what i did and has been working perfectly:
1. set up the extreme N to N only at 2.4ghz and turn on internet robustness on channel 11 with a ssid of DEVO N
2. take the second router and set it up with a static IP (turn off dhcp) and connected it to the extreme N with a crossover cable from port to port not the uplink ports but a standard port to a standard port, set it to channel 1, and gave it a ssid name of DEVO B/G.
i spent a lot of time figuring out how to get the best speeds at my house and i believe i have everything running as fast as possible for me.
if you are interested in seeing my setup you can check it out
http://www.box.net/shared/static/krvm8ii8sk.txt