Currently Im only watching heirs. What are some other good dramas that are airing?
Out of the ones I'm watching I like Reply 1994 the best!
I like Doctor X2 - 6 of ? episodes have aired. (Or have been subbed and uploaded to GoodDrama so far, I should say.)
http://mydramalist.com/article/2013/11/21/currently-watching-doctor-x-2

Today I watched the first episode of Umi no ue no shinryojo. 7 of 13 episodes have aired.

Both are medical dramas, but different from each other! Both are funny, but I'd say Umi no... has more comedy.
Doctor X2 has a cool female doctor. Umi no... has a goofy male doctor, both of them are very skilled.
Lately it's been difficult to find a currently airing drama that can keep my attention. I started Empress Ki and it seems promising but it's 50 episodes.
I second Empress Ki and Reply 1994!
Reply 1994 - totally related to life
I would also say Empress Ki, it's wonderful but there are not many episodes out yet, so maybe you should watch Reply 1994 first
My current favourites are - Reply 1994 - Empress Ki - The Prime Minister And I
the prime minister and i! :)
Golden Rainbow is actually pretty good. Potato Star but they are really slow to sub it.
http://mydramalist.com/korean-drama/7398/man-from-the-stars

Man from the stars starts airing on dec 18, looks good from the trailers ^^
I'm currently really liking Golden Rainbow and Let's Eat. Especially the latter one is refreshing. The focus is on single people (and food) and the humour is a bit more mature than usual in the average drama... My only complaint is that it only airs once a week!
The King's Daughter, Soo Baek Hyang is my favourite drama right now. Also really loving Prime Minister and I :) All the jdramas I've been watching this season are rather disappointing, especially Ando Lloyd. As for twdramas, In a Good Way is having a nice start.