Isobel Crawley was pretty much the only thing that grated on my nerves, which is interesting because I adored her in season 1.
Isobel somewhat redeemed herself in the Christmas episode by talking some sense into Matthew regarding Mary.
And poor Edith! You have to be pretty lonely (and desperate) when your best prospects are (1) a hideously disfigured amnesiac "cousin" or (2) a much older man with a crippled arm . . . .