I don't know a good answer for this question, but people have been considering this trip (somewhat naively, I often believe) ever since this route appeared in the Newfoundland tourism guide. This is partly why I have felt compelled into making this page - to settle the questions and various bits of poor information that have made their way into the previous Trans-Labrador Highway page at the rec.travel archives.
My personal connection to this part of the world was growing up in Churchill Falls from the age of 10 to the end of high school. Labrador generally draws two types of people: those seeking hunting and fishing, or other outdoor sports, and those wanting to get away from the buzz of civilization.
The main draw backs of this region are two very powerful and potentially overwhelming forces of nature: cold winters, and summers of continuous and unrelenting black flies. In the north, black flies do not go away in June, they arrive in June and stay up to late September, when snow is just around the corner again. The huge areas of bog and ponds together with little pollution ensure that the black flies breed in high quantities in Labrador. I missed the black flies by arriving in the brief period of two weeks (early June) after the snow is mostly gone and the flies are yet to hatch. The highs in early June average 10 to 14 - the lows near 1 to 4 Celsius. Because of the black flies, I liked the winters in Labrador better than the summers. Don't underestimate the fly factor - even travellers who have prepared with the best fly dope have been driven crazy by black flies.