Provision to be able to cite SEPARATE sources for different fields of a fact, such as a birth or marriage. Often, a birth date will have a citation from one source, but the birth place cite a different source. Many other events that have a date and place meet the same need. (Marriage, death, burial, etc.)
When citing a source, a button should be provided to "Use the previously cited source." This makes it much faster and easier when citing sources for all the members of a family that share that citation. The window should show what the previously cited source was. (See Brother's Keeper) The same goes for places.
When citing an EXISTING source for a person or event, the drop-down menu of sources should present itself in alphabetical order. (Auto-complete is good, but when you have hundreds of sources, it's hard to remember exactly what the first word of a source was. in order to begin to type it.)
Provide an option for photos: "DO NOT PUBLISH". I would think many folks like to see some pics while using their Family Tree Builder on their home PC, but not want the whole world to see the picture.
Place a small icon in the upper portion of a person's card that is always visible if the person has more than one spouse. As it is now, you must scroll down to see if a person has other spouses.
Show the divorced date in the "status" block under a couple. It's currently shown for marriages, should also be for divorces.
That's all I can think of for now. Maybe more later.