Comment 3 for bug 1181155

I guess the original reporter uses Neutron.
When neutron is used, an operation of associating floating IP to an instance is an API call to Neutron.
Nova seems to sync network related information with neutron (quantum) periodically.

I confirmed floating IP associated is not listed in the instance table just after associating an floating IP, but after waiting for around 30 minutes I saw both fixed IP and floating IP are displayed. (Grizzly and Havana have the same behavior.)

It is ideal to display associated floating IP just after associate operation, but it is an acceptable limitation.
In addition, the problem the author pointed is "it is impossible to remember unless you note down somewhere" and we can see floating IP addresses in the instance table and detail page if we wait after less than one minute.
(Note that we can see floating IP is associated in Floating IP table in "Access and Securtiy" even just after association because information is retrieved from Neutron.)