Are any of the uses particularly useful?
I'd say that all four uses are useful, but in different situations;
* It's just like Intimidate or Con, except rather than threatening or using deception you're using a position of authority to get a NPC to do what you want
* Similar to the diagnostics power from a machine sprite, you may use it as teamwork skill without knowing the specific skill you are assisting
* You may inspire
the entire team to get more dice to resist a surprising situation
* You can use it to increase the Initiative Score
of your entire teamDo you think a character built around maxing it out would be viable?
Are you asking if the Face archetype is viable...? (yes it is).
how often would that be effective?
With the use of supporting skills such as Impersonation and Disguise the skill can be extra useful during the infiltration phase of a run against facilities that have guards that are used to follow the chain of command (note that in some situations Intimidate or Con will be better options, but with a Charisma build you often get all 3 skills anyway). Leadership increase the chance your team are not surprised during an ambush (which is useful in almost every surprise situation). Leadership may be used to increase the dice pool and limit on a single test that any of your teammates take (which is useful pretty much always). During combat Leadership also increase the Initiative Score of your entire team (which is useful every combat turn).
On a related note, how does the leadership work with surprise? Inspire works on the team's surprise test, but how does that work? Would you have to make your inspire check as an immediate/free/out of initiative action before anyone rolled for surprise? Am I just missing something obvious?
That is actually a really good question.
Personally I don't see how rolling for Inspire
after people already became surprised and lost their initiative score would be resolved. Except maybe in the corner case where the leader have really high reaction + intuition (so they are not surprised in the first place) and really high initiative score (so they can use Inspire
before their teammates acted in the first combat phase). Also, would teammates get +10 initiative score retroactively if the extra dice from Inspire mean they didn't become surprised in the first place...? It is kind of a mess if you ask me.
I always just played it out as: "I am keeping the team Inspired in case we walk into a surprise situation" and just resolved the surprise situation by:
1. Roll for Inspire.
2. Roll for Surprise.
3. Roll for Initiative.
So even if the Decker has 15-20 dice for hacking, you can kibitz what she's doing and still give her more dice to use even if you don't know the difference between hot sim and cold sim. Even if the mage has 15-20 dice for conjuring spirits, you can give him more dice by "leading" him through the summoning even if you don't know the difference between mages and shamans. Etc.
Leadership used in this manner is not so much about "leading the target through the hacking or summoning process" as it is about coaxing, convincing, threatening, or challenging the target... you are building confidence, removing fear, relaxing, inspiring and/or triggering the target. You make the target more focused.
Similar to that a 2018 scrum master doesn't really need to be a software developer, but he or she can still use his or her servant-leadership skill to inspire and challenge the scrum team to deliver working software, faster.