I also have a Vermont Casting's Merrimack installed in my home in Southern Maryland right on the Potomac River. The house is a poorly insulated 2000sqft single floor cottage style home with a living room that is about 26'x14' with about 16' of windows lining the wall facing the water. The Merrimack is on the opposite wall. Needless to say, those windows create a very chilly family room, but the Merrimack definitely solves that problem. I have found it adequate to provide about a 30-40 degree temperature differential between outside and inside at a reasonable burn rate (say fan at 40%, mature fire, damper in lowest airflow position). By temperature differential I mean that if it is 30 degrees f outside then I can keep it about 70 degrees f inside.
I do experience mildy smoking of the glass, but only when it is being under-fired. If you keep it roaring and hot the glass is very clear.
The most significant issue I have is the noise generated by the blower. I actually think I may have a defective blower because it is so loud. I will contact Vermont Castings to verify... anyone if there is anyone out there who is a sound / audiophile and can take decibel measurements I would appreciate comparing notes.
For the measuring setup, the fire is roaring, the fan is on and I varied the speed by percentage (left colum), the right colum is the decibel A weighted measurement at a distance of 15" from the the front of the Merrimack. The measurements were taken using a RadioShack sound level meter that I trust and routinely use to calibrate home theater surround sound systems.
Here are my rough sound measurements:
Fan Speed - Sound level
10% - <50dB-A
20% - 52 dB-A
30% - 54 dB-A
40% - 55 dB-A
45% - 57 dB-A
50% - 59 dB-A
55% - 60 dB-A
60% - 62 dB-A
70% - 64 dB-A
80% - 65 dB-A
90% - 67 dB-A
100% - 69 dB-A
For a reference on sound equivalents in decibels, see this wikipedia article:
http://en.wikipedia.org/wiki/Sound_pressure#Sound_pressure_level
The bottom line is that anything over 55dB-A in your living room is going to be VERY annoying. 69dB-A is equivalent to listening to a loud electric mixer in your living room all day long... not pleasant! This is why I think mine must have an issue, I couldn't imagine this design would get past the testing stage.
I will provide an update when I hear from Vermont Castings. I suppose it will also be a test of their customer support!
If you are interested, I posted a Youtube video of mine with the fan running at full speed, I am sure you will agree it is a bit ridiculous!
http://www.youtube.com/watch?v=Ibmz8PqcjBE
I must admit that I love the looks of this thing though. If the blower doesn't have an issue and this is just how loud it is, I will probably design and fabricate a replacement for it myself.