The scenery is fantastic: loved the King's Roads. (CG or a location?) The cameo with George III was excellent, and him appearing in the middle of the road on what looks to me like a blasted heath was a lovely bit. Norrell is and is not as revolting in the series as in the book; one never knows whether to sympathize or not.
Do not like the characterization of Drawlight, which is overdone. Certainly do not like the Gentleman, who is a totally original character. On the nitpicky side, I always thought of Segundus as round and middle-aged, not a romantic young man.
More importantly, am with kate_nepveu that Stephen does *not* have a bargain with the Gentleman: saying yes to an invitation to a party does not imply consent to whatever terms it is the Gentleman thinks he's agreed to (which no one ever tells us that I can see.) I'd have liked a Stephen who was less a weary helpless victim, trapped as much by his self-image as the consummate servant as by the Gentleman's whims: though in the book Stephen uses his butler's skills to talk the Gentleman out of his more bloodthirsty schemes, which is how servants traditionally finagled the system so it worked at least a little less against them. Stephen who's voluntarily made some obscure bargain with a person he doesn't know goes down a lot less well.
But mostly it's Stephen and Lady Pole that bugs me. Naturally they're linked; presumably Lord Pole has no one he trusts as much as Stephen to see to her welfare, and so we always see them together. But it feels totally *off* that Lady Pole is sent north in company of three men, completely unrelated to her and of a completely different class, without a female servant or chaperon or you name it. Sorry, that's just Not Done.
(As ever, these spectacles elide the presence of servants. Lord Pole would appear to have none at all except for his butler and a maid or two. No footmen, no body servants, no one in the public areas of the house should he want to send a message. Stephen has to answer all the bells himself.)