My network consisted of two SMC Draft-N Access Points (at each end of the house) in bridge mode, all connected via a Gigabit switch.
When transferring .mkv files from my NAS to my laptop or vice versa, the transfer speed was quite poor so I decided to try a dual-band router as my X220 supports 5.8GHz wireless. I purchased two Cisco EA6500's but only ended up deploying one as the range was so good.
It's important to note that although the new EA6500 supports 802.11n and 802.11ac on the 5.8GHz channel, I elected to just enable 802.11n as I do not have any 'ac' adapters yet until I get my new Galaxy S4 (or the HTC One). I split the networks in two so that I had dedicated 2.4GHz and 5.8GHz SSID's.
As you can see, simply switching from 802.11n @ 2.4GHZ (on the SMC) to 802.11n @ 5.8GHZ (on the EA6500) made a huge impact on my transfer speeds. Of course, you need to make sure your devices support the 5.8GHz band for this to be useful. My iPhone 4 doesn't but the Apple TV 2> does.
The before and after transfer speeds are shown below. Well worth the upgrade cost I'd say!