Currently you can add any field you want to the user fields section, and you can apply conditionals like you can on any entry field. But the conditionals don't operate in real time and the user doesn't see the conditional field until they hit save. Another downside of this is the save brings you back to the first tab and so the user doesn't see the change unless they click back into to the user fields tab.

Its clunky and not user friendly for the user to keep saving for conditional fields to appear. I presume this is because auto save isn't enabled like on entry fields so the conditionals don't work in real time.

I use the user fields for staff profiles in university, and we have around 50 fields that the user can fill out. Not all fields are relevant to all users so having conditional fields operate in real time would really improve the process of creating a staff profile.