I suppose you're looking for real life experience, I don't have any yet and am curious as to what others think about the question, but I can point you to some docs to read in the meantime.

Check out [url]http://technet.oracle.com/doc/oracle8i_816/server.816/a76992/toc.htm[/url] , you'll need a free technet registration. Just look for the sections on Bitmap Indexes, Clusters, and IOTs, I didn't see one place comparing/contrasting the three, but you can read all the 'when to use' and 'when not to use' of the three individually.