I started playing about 6 months after Beta ended. For my first 1.5 years, always thought 'sin/Shadow was too hard and felt odd. Then it fell together for me. DPS 'sin has been my main for over a year, almost 2. Leveled as Deception.
During DF HM progression, had several people tell me I could up my DPS by switching to Madness. While I had played a Madness Sorc, I was doubtful. Changed anyway, and carried over to Hatred with 3.0. I love the spec.
I do some PVP, but not enough to be in Ranked, much less on the boards. So now, my favorite toon and favorite spec are questionable if they will be usable in HM content, which is exactly where I am headed. Great.
I am not about switching toons just to have the best DPS, I do what I find enjoyable. So my enjoyment of the game is getting nerfed. I am going to try to tough it out with Hatred, but from what I have read here, I am doubtful. Very sad.