The gain in speed from G to N is not so much for the Internet as for your LAN activities. I got a real improvement for things like streaming media from my Media Server, file transfer etc to my laptop. Some of those things will work OK using G but for bandwidth heavy activities AND portability, N is the way to go.
I like to watch DVD quality

files rather than higly compressed AVIs over my network from my NAS. My G wireless router couldn't cope with this, video would stutter and break up, the upgrade to N fixed this nicely.
I use a Linksys Wireless-N Gigabit Router in combo with a Linksys Gigabit switch for the house LAN.
If a mix of wireless devices (N & G mixed mode) are connecting to your N router, the slowest device will set the speed for all
wireless devices i.e. your N device's throughput will be degraded.