Watched it three days ago - and I keep thinking about it.
At first, I wasn't impressed with the biographical story line. I knew in advance that Turner was a painter and that Spall got kudos for his acting - but nothing about Turner's personal life. I was confused about Turner's father for a few minutes - the actor didn't look that much older than Spall!
Honestly, I would have gotten more out it if I had read up in preparation.
Still, I thought it was beautifully filmed and think it's worth a second viewing.