Checking it Out
Once you have the 900AP+ programmed, you can unplug it from your LAN and move it to the desired location. Remember that the weakest link in the wireless chain will determine the overall throughput of the repeated connection. You don't want to locate the repeater so far away from your main AP that it has to drop down to a lower speed to maintain connection. On the other hand, if you don't move far enough away, your client may keep trying to hang onto the weak main AP signal, rather than switch to the stronger signal of the repeater.
The 900AP+ doesn't help you much during this process, since its WLAN light constantly flashes wildly away, even with no data flowing through it. And since you can't access the built-in Admin function via wireless connection, you can't use the Site Survey tool that D-Link added in the new firmware.
I ended up using my ORiNOCO card and NetStumbler to tell whether I was associating with the main AP or the 900AP+, since XP's built-in Wireless Network Connection status was no help. I did find that using XP's Connect to Wireless Network function (via View Available Wireless Networks), selecting the network, and clicking the Connect button when I was closer to the 900AP+ than my main AP caused my client to switch over to the 900AP+. I confirmed this via NetStumbler and also by using the Signal Strength indicator in XP's Connection Status window. You should be able to do the same thing using your adapter's client software if you're not running XP, or choose not to use its built-in wireless management functions.