As shown in the Advanced page screenshot, the 5450 can perform bridging and AP client mode tricks. However, I was unable to find out from USR if the 5450's bridging is WDS-based. They did say that the Group AP choice is intended to facilitate IP Roaming among several Access Points by creating a "Group" of Access Points with one AP acting as traffic control manager.
The HTML "manual" has clear illustrations of the setups for each of the bridging modes (and AP client), but didn't contain detailed setup information. In my experience, setting up bridging is tricky - mainly because every vendor puts a different twist into the settings and nomenclature - and step-by-step instructions are a must.
I had neither multiple 5450s nor detailed instructions, but gave it a shot anyway, attempting - and failing - to set up repeating with a WDS-based Buffalo-Tech WLA2-G54.
Two other features of note are the very helpful Log screen shown in Figure 5 (reached via a button at the bottom of the Status page), and the fact that SNMP management is supported. You'll find SNMP setup controls on the Tools page.