I am surprised there is no thread about Downton Abbey - a classic masterpiece with humour that is thoroughly enjoyable.
In the first episode I thought there were too many characters and too much going on (slightly hard for my wife and I to follow with our young daughter in the room). After a couple of episodes I really started loving this high quality eventful drama. The second time I watched series 1 and 2 I was able to better appreciate/notice all of the humour - much of it subtle. For a classic drama it is at a quicker (better) pace than other classic dramas.
This is the best drama I have ever enjoyed, although there is plenty of sadness (set around the early 1900s before, during and after the First World War), the characters are fantastic and the wit is simply brilliant.
It includes the legendary Maggie Smith and many other terrific actors. A couple of actors from sitcoms: Penelope Wilton (Ever Decreasing Circles) and Nigel Havers (Yes Minister/Yes, PM).
It reminds me a bit of the sitcom You Rang, M'Lord? (one of my favourites).