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Ok, well on the router that the link failed, if it actually goes down, there's link debounce time, which varies, before the interface down is reported to the routing. If the local interface doesn't go down, there's the OSPF dead time delay.
Then with Cisco's OSPF, and the IOS version, there's a configurable delay before an LSA is broadcast, there's a configurable delay before the receiving router will process the LSA, there's the time it takes to run SPF (which varies based on complexity of topology, speed of control plane processor, and options like iSPF), then there's the time for multiple routers to converge. (NB: on some of Cisco timer's, there's additional configurable delay if there are multiple LSA within a certain amount of time.)
All of the above, together, might be under 100 ms to over 40 seconds.
PS:
With timer tuning, and fast detection of link outages, you might be able to achieve subsecond convergence.
Also if you have multiple equal cost paths, fail over can be in SONET time ranges.
