If you're into twisted dark serial killer thrillers this show is for you. It reminds me of The Killing, except probably better. I recommend it if you can get past Gillian Anderson's terrible British accent.
Series 1 was very good. Not so hot on series 2 but still well worth watching. For me, I had no issues with her accent. Didn't seem that bad to me. Certainly endured far worse.
I always found this very uncomfortable viewing, but it is well done. I thought her accent was pretty good. If I hadn't known that she wasn't English, I'm not sure I'd have noticed.