When we got married, I did not change my last name.
I was asked (and still get asked) when I will 'decide' what to do about my name. And that's the thing, I decided at the time, but for some reason as I didn't take my husband's name, people assume I just haven't decided to do so yet.
I have a few reasons, some more sensible than others:
1. I have had my name since I was born, and as I am still essentially the same person, I'd like to keep it that way
2. I don't like the way my first name sounds with his surname
3. My surname is quite unusual and is at the end of the line in my part of the family
4. As someone doing a PhD, my surname has begun to define me academically, and being unusual it's a good surname for someone in academia to have
Don't get me wrong, I actually like receiving personal mail to Mr and Mrs X, as we are a unit, but I still keep my surname for most parts of my life. And I'm planning to keep it that way.
The only niggle in my mind is what to do when we have children. Hyphenate? Use my surname rather than his? Use my surname as a middle name? Exclude my surname all together? And this is where I can't decide. But for now it doesn't matter. I can keep my name and be happy with my decision.