FurryNutz, thanks for pointing me in the right direction. I get that there's a movement to simplify the user interface for a lot of things, so after using the venerable DIR-655 for nearly a decade, the pretty diagram confused me.
I've now had a chance to complete the configuration of the DIR-885, and it's now in service. I did a before and after WiFi survey of the apartment (using NetSpot) and the signal is noticeably stronger in many locations. Furthermore, doing a speed test shows that the WiFi is no longer the bottleneck when it comes to our internet connection (6 Mbps DSL). Very pleased with the router over all.
The only minor issue (for me) that I came across while configuring the router was the IP address space used by the Guest Zone. The DIR-655 uses 192.168.0.x (same as the local network). The DIR-855 uses 192.168.7.x (seems like an improvement to me). This is not user configurable for either router. In my case this latter IP address space (192.168.7.x) is used as part of my network's double NAT setup. [Yes, I know, double NAT is bad, blah, blah, blah,.... Had to use it for historical reasons, blah, blah, blah,.... Long boring story, blah, blah, blah,....] It was easy enough to get around, but required changing several port forwarding / virtual server settings in the DSL modem. Net net everything is working fine.
Once again, very pleased with the router.
Larry ....