Surely it means if one channel gets interference the other stands a chance of compensating?
Yes - but you potentially take out a channel a neighbour could be using for G, with your attempt to get faster speeds.
Its an issue to me as I'm in a block of flats. I've had WiFi since 2002, and in 2008 I started seeing other networks appear, and there are now almost a dozen. Many are overlapping. Performance of my single channel N connection was equal to wired - on my work laptop (Intel 5100 wireless) which states "65meg" most of the time. However I'm now seeing lots of interference causing retries so data rates over wireless at 4meg.
Dual channel doesn't help this. The old 802.11a band at 5.4ghz does help, if all equipment is compatible. Many routers offer 2.4 or 5.4 switchable - what we need is both for legacy devices and new devices to interoperate, so that handheld devices that aren't N compatible don't interfere with equipment that is.
The way I read it, you could be right about slight unfairness, but the interference effect is to (at worst) knock out one channel that may still run at 130Mbps. 130 > 54?
Its only "unfair" if you're using two channels in a road / block where channels are in demand. If you're in an open area you should be fine. inSSIDer is the friend here
pro - on THFB - sync about 17.2mbps - BQM