I get that question a lot. I was the first of my college friends to get married. It all happened so fast that it was like 'giggling with my girlies as we snuck away from the scene of a party at 7:00 am and random hookups' one week to 'holy crap, I'm registered for wedding presents' the next.
I think, at least with my friends, the questions they were really asking were:
1. Are you suddenly different?
2. Are we still BFFs?
3. Are you really happy? If not, I'll bust his kneecaps.
4. What made this one different?
5. I want to know what it feels like to be married, tell me all about it.
My answer is, honestly, I don't feel any different. That's how I knew he was the one! We were married from the second we laid eyes on each other. If it's someone I'm not as close to, I tend to say "It's brilliant, I get to be with my best friend every single day!"
for the record, I've been married for 3 1/2 ish years. and I still get asked that! (the baby questions have started creeping into conversations now, too)