The movie was much like the series, with a greater variety of establishing shots of Highclere Castle. Highclere at night. Highclere seen from the town. Highclere from a drone.
There were a few differences. Butler Barrow has forgotten about the torrid affair he had with some upstairs fellow in the first season. Bates has forgotten he has a limp. Violet has forgotten how to be biting. (It was a shame; they used up all the good Violet lines in the series. In the movie she just says petty things in a biting way.)
All the upstairs drama had entirely too much ex-chauffeur Tom. Tom, Tom, all the time. The Tom Show.
The downstairs drama was actually pretty amusing, in that the staff all join in their hatred of a common enemy. Sadly, I sided with the enemy. Think about it. You just can't risk poisoning the king. Gary even agreed. We are Royalists in our disdain of Tom and defense of the King's staff.
One final note for Julian Fellowes: don't have a dress makeover and then hide the reveal until halfway through the final big scene. That's just wrong. What if Scarlet pulled down the curtains and then her green dress didn't show up for hours? What if Maria cut up the curtains and you never saw the Von Trapps in them? No. Nothing that dramatic happened, but there is some tailoring that wasn't finished as swiftly as I wanted it. A dress makeover demands a quick turnaround.
I did enjoy it in general. I got weepy in the spots I was supposed to. It did its job. Required for series fans, I think: anyone else could skip it.