Let's look at how WPS is actually implemented, starting at the AP side of things. Figure 1 shows the Wi-Fi Protected Setup page in D-Link's routers.
Figure 1: D-Link Router WPS settings
Figure 2 shows the Wi-Fi Protected Setup screen in the Belkin N Wireless Router (F5D8233-4).
Figure 2: Belkin WPS settings
Both have a general Enable, which is set by default and both show the Router PIN, let you generate a new one or reset it to its default. But the Belkin takes a one-screen approach, letting you enter a client PIN for a PIN session or start a PBC session. You also can see the Configuration Status, but unfortunately, not reset the router to Unconfigured. We'll see how important that is later.
D-Link takes a multi-screen approach, making you go to the General Status page and scroll down to the Wireless LAN section to see WPS status (Figure 3).
Figure 3: D-Link WPS Status
Starting either a PIN or PBC session requires a click on the Add Wireless Device with WPS button on the Wi-Fi Protected Setup screen. This launches a wizard shown in Figures 4 - 6. I think this is overly complicated and prefer Belkin's one-page approach. All Belkin needs to do is add a Reset to Unconfigured Button to their screen and they'd have everything in one place.
Figure 4: D-Link WPS Wizard - Step 1
Figure 5: D-Link WPS Wizard - Step 2