How do you use the Federated Storage Engine?

We are looking for community feedback on the use-cases for the Federated Storage Engine in MySQL.
Specifically, I would be interesting to hear which users find that the introduction of multi-source replication meets (or does not meet) their requirements.
For a bit of background:
The Federated Storage Engine was introduced in 5.0, but has long been disabled by default. It is useful for ad-hoc queries across MySQL servers, but it misses some of MySQL’s newer optimizations, and does not perform as well as we would like. Among it’s limitations it also does not support transactions.
By using multi-source replication, many of the downsides mentioned above are negated, since the tables can be made available to query locally. The disadvantage of course, is that there is a need to provision more storage (however, given the performance limitations of federated it is not certain it could fill this use-case either).
So please leave a comment, or get in touch. I would love to hear how you are using the Federated Engine, and what you plan to use multi-source replication for.