Nobody was surprised.
My ex, who is also a good friend, said that now I mentioned it, there were always 'signs'. He wouldn't have figured it at the time, but as it was now known, looking back he saw the obvious signs.
Some friends didn't miss a beat and did not care at all.
One or two asked me if I was 100% sure, and that I wasn't having some kind of crisis in my life. But they accepted my answer that no, there was nothing new about it for me. One warned me against hormones because in his experience (he is part of the LGBT community himself) he didn't think the results he'd seen were necessarily that great. I'm not sure if he was referring in general to all trans people, trans women or trans men at the time. In any case I was already quite sure I was going to take T, and it hasn't been mentioned since. Quite a few of my friends are ex-military and they were the ones with the least questions or concerns about it. As tends to be the case with military guys I know, they know the difference between actual crises and emergency situations and things that just aren't worth losing your rag over. So to them it's nothing worth caring deeply about. They haven't changed the way they interact, we still joke mercilessly with each other and about everything else and provide a certain kind of straight-up moral support to each other.
Basically it's gone unchallenged by every one of them. The only person who had beef with any of it was my mother, none of my friends have altered the way they act or talk to me in the years since. Which means that I was never really treated as female. My personality didn't much allow for being treated that way, so either they maintain a neutral sort of attitude toward me, or a male to male one. My female friends generally treat me as they do their male friends. They don't for example, tend to tell me in detail how much their boyfriend happens to be annoying them... in the distant past they would often tell me all about their guys, and other things that bothered them. Of course I could understand it to an extent, I could understand both sides... but now I am not the go-to for advice, their girlfriends are.
I told them, about 4-5 years ago now, but I didn't demand they start calling me this or that. They all came around by themselves to referring to me by male designation, which is interesting.