Windows 7 - Maximizing wireless LAN speeds

So, I've just tested a large file transfer over my GigE network which maxed out over copper at about the sustained transfer rate of my source drive: ~70MB/s. This is to be expected, and I'm content with it. I'll check it from SSD to SSD when I get a second SSD drive. But, what irritates me is that wireless N barely out performs G. I'm getting about 9MB/s from a wired system to my wireless, on an N connection. The same source and data folder that transfered at 70MB/s via the same router. Its transferring to my 5350 intel WiFi card. I realize local interference is an excuse that intel/wireless-N could use to lessen expectations, but - is this it? The theoretical is 35MB/s of which its getting 25%. There's no other claim in the PC world that falls as short as this if this is really what N can produce. Minimum should be half, and standard should be about 75%. What's the point of reporting the theoretical numbers if it in no way performs relative to it? Is there anything I can do?

Destination (since source is performing adequately) is:

Windows 7
Intel 5350 N capable, claimed to support 3 spacial streams at 450Mbs
Buffalo Tech's WZR-HP-G300NH - claimed capable of 300Mbps
Distance is >20 feet (~15)

Is there anything I can do to improve this? Or am I supposed to be happy with this?

You could try switching channels to see if it is interference based. I never rely on wireless devices for anything other than connectivity. Speed is never very good in my experiences. So, whenever I do a substantial download or file transfer, I always do it on a hard wired connection.