I actually own the medium version of this frock coat now so I'll throw in my opinions.
The fabric and just general design of it is fine in my opinion. Some have complained about the lapels but that doesn't really bother me. The only part of the design that I'd alter are the cuffs as they are non functional with the buttons just sewn on for show, the screen used one has working cuffs.
The sizing is the main issue, I'm not far off Matt Smith's build (6'2 and 38L jackets) but the medium is far too big on me. The sleeves are about an inch too long and I can make the front overlap to be double breasted around my front, whereas frock coats are supposed to be very fitted. Basically the medium is really designed for someone who wears a large. I intend to get a small for myself in the future. If you are between sizes I highly recommend getting the smaller one.
That being said it's a great garment, just make sure you get it in the right size. Email AbbyShot if you're unsure and remember that it runs large.