My world is always easy to build. It's the one that's right in front of my face, though I do add a few extra features.
Since I tend to write people that I already know, ones that I'm comfortable with, my is the one that I already inhabit. My heroine has a facebook account, my dashing hero a motorcycle (much like my husbands, hmmmm), my characters have mortgages. That doesn't make the world I write boring, just more realistic.
As a reader, I love the books that you can get lost in. But the ones that have too many fantastic elements, ones that you have to remember what is in this world and what isn't, usually loose me within the first hundred pages. I guess I like to have a healthy dose of realism in my fantasy.