When I started my age-gap romance during NaNoWriMo, the words just flew out of me, and I produced 28, 727 words in the span of seven days! The idea gripped me, like plot bunnies used to in my early years of writing when I worked on fan-fic etc.
Just after NaNoWriMo I got sick, so didn't do any writing, then I got swept up in holiday prep and the kids being off school for Christmas etc. so no writing got done, then, either.
I got back to it yesterday, and managed 2444 words - not as good as when I was producing 5k during NaNoWriMo, but back on the right track, and hopefully once I get into the swing of the story again, words will start flowing in massive amounts.
So yeah, on the whole, for a first draft, this one is pretty easy. Obviously, there's minor blips, like in any story and sometimes real life takes over, but on the whole I have a good understanding of the characters, and know exactly where the plot is heading. I feel confident I'll have this finished soon (I don't want to give an exact date, as February will be busy for me with the release of ALL IT TAKES), and I'm fairly certain editing and revisions won't unearth many major issues.