This is what I've seen:
SAs hate:
1) people who demand a Birkin, then get upset when told that there isn't one available (IME, they don't get upset when they're asked politely about it)
2) people they don't know who ask for a Birkin to be brought out "from the back"
3) celebrities who invite a media frenzy and disrupt their loyal customers who are trying to have a pleasant experience at the store
4) rudeness, in any form
5) people who take a "dainty" attitude toward their items, like not using them for fear of what may happen to them or, worse, bringing their bags in and having a fit over every single little scratch or dirt mark
SAs love:
1) loyalty
2) friendly chats, especially when they get to discuss topics not related to Hermes (many of them have outside interests, too, just like the rest of us)
3) appreciation for Hermes items other than the Birkin
4) people who actually use their bags