I have a 13.3" MacBook (Black, OS 10.6) that is a previous generation (before the new aluminum 13" MacBook Pro). Besides doing a file transfer test, how can I verify that my MacBook is connecting at N speeds rather than G? In Windows you can tell using the popup from the Wireless icon, is there an equivalent for the Mac?
Since you are running 10.6 Snow Leopard, hold down the Option key and click on the wireless icon in the menu bar - you should see extra details about your wireless connections now.
Under "PHY Mode", if you are connected via N, you should see "802.11n". If it's "802.11g", then you are on the 54Mbps G mode, and so on, and so forth.
Also, you will see the rated speed under "Transmit Rate" - on a G network like mine, it will say "54". On an N network, it should (cannot confirm) say "540" or something.
Please take note that "Transmit Rate" is not equivalent to real transfer speeds - it is only the theoretical maximum. For wireless, the actual speeds are usually less than half of the rated speeds.