Some of them include: lifecycle methods, postback indicators (i.e., being able to tell if this is the original request, or a postback), routing capabilities ("return this view if the principal is in a given role"), security, and configuration outside of XML.
Even a short consideration of annotation possibilities within JSF raises more issues than I care to think about. However, there is no doubt that some areas such as security, where the linkage problem is not an issue, could be a very effective use of the annotation technique. I would certainly like to see the Expert Group address some of these possibilities in the future, hand in hand with the perhaps more important issues such as process scoping and sub-flows.
Are annotations the right way to go? Are there more opportunities for using annotations that you can see?