The key thing to understand about the DIR-655, and any Draft 11n Wi-Fi Certified product, is that it must default to operating with a 20 MHz channel bandwidth in the 2.4 GHz band. That default is intended to make draft 11n products play nice with legacy 11b/g products.
This doesn't mean that you won't be able to set draft 11n products to operate with a 40 MHz channel bandwidth in the 2.4 GHz band. In fact, the 655 allows this via its Auto 20/40 Channel Width setting. But other products, such as Apple's AirPort Extreme Base Station, may choose to lock out 40 MHz operation in 2.4 GHz entirely.
This stopgap measure still leaves plenty of room for manufacturers to produce products that operate in odd and low-performance ways over the next year or so until the 11n spec is finalized. So don't expect even Wi-Fi Certified draft 11n products to be trouble-free. See my blog post on this if you want more info.
The 655's main wireless configuration screen is shown in Figure 9 and reached via the Manual Wireless Network Setup button on the Setup > Wireless Settings screen. Modes supported include the Mixed 11b,g,n (default), b, g and n only and mixed b/n and g/n.
Figure 10: Wireless Setup
The Enable Auto Channel Scan "automatically finds the channel with least interference" according to the online help and it seemed to work the few times I used it, at least in 20 MHz mode. You can also disable it as I did and manually set the channel. But note that the user interface does not indicate the extension channel used in 40 MHz channel mode, which I found somewhat misleading.
Tip: The 40 MHz mode Extension channel is always located four channels away from the Primary Channel. So if the primary channel is set to 1, the Extension channel will be set to 5. Note that for higher Primary channels, the Extension will be below the Primary.
The Transmission Rate selector offers a dizzying array of transmit rates for b, g and draft 11n rates, the latter indicated by the MCS NN labels. These Modulation and Coding Schemes are defined in the Enhanced Wireless Consortium's (remember them?) PHY spec, which can still be downloaded (PDF) from the EWC website.
The Setup > Wireless Setting screen also holds buttons for the Add Wireless Device and Wireless Network Setup wizards. They're not very wizzy, since the former only deals with devices supporting Wi-Fi Protected Setup (WPS) and the latter produces only the relatively unhelpful screen shown in Figure 11.
Figure 11: Wireless Network Setup Wizard result
I couldn't test the Add Wireless Device wizard, since the DWA-652's Draft 2.0 compliant driver works only with Windows Zero Configuration, which doesn't support WPS. But then again, neither does the client program that comes with the DWA-652 card—the Cardbus companion to the 655. If you do have a card or device that supports WPS, however, the 655 can allegedly handle both PIN and Push Button methods.
The Wi-Fi Protected Setup screen shown in Figure 12, provides a few more options, such as locking wireless security settings and changing the PIN that is used with one of the WPS methods.