It went exceptionally well. They just introduced me as a new hire, even though I've been working with these people for 10+ years across two companies. A couple asked me some questions afterward. One wanted me to go to lunch with them and I went. Two of them seemed to give me the evil eye. One of those two later came up to me and told me they wished they had my courage. My boss just said, "You only live once and if it makes you happy, do it."
As far as overall reception, they switched to using the new name the same day I told them. With the exception of the two people that asked me questions, nobody has asked any questions at all. It's like they've always known me as the new name and it's business as usual.
For the bathroom thing, upper management said there's no issue and anybody that did have an issue with it would have to get over it. I still ended up using a bathroom on a less populated floor. The staff wasn't notified of management's position on the bathrooms, so I didn't want to push it.