This is a pretty awesome style. The rugged mane style really adds to the drawing immensely. I can't yet decide about the eyes though... They look both, pretty awesome and kinda....creepy/flat? Something? I can't really put my finger on it. Also, it might be only me, but chest hair looks weird for what looks like a mare, and not a stallion (judging from the eyelashes). And I think you forced a bit on the FLUFFINESS of the ear xD.
But overall, I love this. It's something way different than your other works and give the pony characters a more realistic look and this one especially looks like a real portrait drawing that a person would request from a painter to do.
I personally think its amazing, absolutely amazing. I'm not really a artist myself, ad I'm a bit jealous. It gives me a feeling, even though I have no idea what that feeling is, sorry. The ears are really cool with the extra fluff, and the chest hair is kinda ok. The hairstyle is so funky and rugged (me like it). I hope you do something as splendid as this soon.
By the way, I'm sorry if this ain't much of a critique you would expect. (><)/
One more thing before I end this weird critique, the eyes are really, really cute.
The ONLY fault I can see here is the eye in the background... the right eye. You make the pupil and eyelid really small, when it should match the size of the other one, and be hidden by perspectives and things. It should be smaller because it's farther, but not that small. Both eyes should be on the same level of the face.
But perspective is really hard. And eyes are really hard. And I can't really judge either. But yeah...
But overall in style, I really like it! Good work!