A couple of suggestions:
1. Currently, if an event is without date, it is put at the end of the timeline. What really bothered me is the birth, which clearly should be at the top in all conceivable situations. Geni could be smarter by putting birth and death (and burial) at the top and bottom, and other events (with or without dates) in the middle. Marriage should, as the default, appear before the birth of the children. The order of children's births should agree with the birth order, if available. It would be even better to have an "event order" just the way birth order and marriage order are handled.
2. Allow merging of events. What I can think of include death of multiple people in a single event, death of the mother in childbirth, birth of twins, siblings or cousins going to the same school in the same years, etc. Adding people inside an event does not really resolve the problem.
3. View other family's timeline. It's good for both relatives (in-laws) and historical profiles. And a list of families (i.e. family names)
4. I would prefer to have months in short form, or in numerals. And, make it translatable through tr8n.
I also dream of a different layout for timeline, one that you see in books. A horizontal line correctly depicts the time scale, with boxed texts above and/or below. Some kind of hovercards would be cool too. Maybe color coded for different types of events. Family timeline can have other fancy features like showing the lifespan of each individual, though an obvious problem is that there are easily too many people.