Would be nice to have to ZD supply DHCP for guest SSID's so you don't have to use up your production network IP addresses. With all of the BYOD stuff you can run short. I know that Vlanning is one way but for those who do not have that ability this would be nice. Just saying that the competition has a controller that will do this.
I use DHCP reservations only on my in house servers with no available free DHCP addresses in the scope. That way the only devices that get DHCP addresses from them are pre-configured devices I want on my work subnets 192.168.0.XXX - > 192.168.3.XXX. I let the ZD hand out addresses in subnets 192.168.4.XXX -> 192.168.5.XXX for everything else (ZD has a 500 max capability). Firewall rules help keep the traffic isolated.