I remember the first couple months I was constantly walking around thinking "is this what sober feels like? am I normal right now, or am I still weird?"
I guess one of the surprises for me has been that normal is so... not normal! I just had no idea (or had completely forgotten, more accurately) how many different moods and states of mind one can go through without any substances or even external factors. I still find myself kind of amazed when I do something really absent-minded or impulsive and think the next day, "huh! and I was sober!"
Or, on a more positive note... and this only began happening in the last month or so... I'll be doing something I enjoy or laughing with friends or listening to music and I'll just be thinking, "I feel drunk! I'm dead sober but I could almost swear I'd been drinking!"