Though I am sure that this is a quite and peaceful river in the warm weather months, I have been lucky enough to join a group of 20-30 slightly insane guys that decide a few days of camping out and paddling over a weekend in the middle of February is a safe idea... they have been doing this for twenty some odd years!
In all honesty, I have been fortunate enough that the last two years have been around freezing and the weather has been down right perfect considering. I have heard the stories of previous years of sideways wind and snow and sub-zero temperatures but I have yet to experience(at least on this river).
The best part of running the river in the middle of winter is the fact that the river hasn't been cleaned since fall. All of the trees that have been knocked over in the previous months are still there. The river, depending on snow/melt cycles, is either peaceful or "a little nerve wracking." Regardless, the smallest rock garden becomes one of the scariest things in the world when you have the fear of taking a dip in below freezing water(and trust me it happens). You constantly have to wonder when you take a beer break on the shore if that first step on to the snow covered ground is actually terra firma or an ice shelf that hides hidden depths below.
With the amount of people on the water that there is, if you do end up dumping you can know that you are at least slightly safe... as long as you don't stray to far away from the pack, if you do take the unfortunate plunge there are multiple people that are willing to risk their life to grab you from the water. At least two people will be on shore already lighting a fire to help dry you out and there is always somebody pulling out a flask in a vain attempt to numb the pain(be there a swimmer or not). Fortunately for everyone's ego, at least 10 guys ready to laugh their asses off and take pictures as soon as they are sure that everyone is safe.
As I said, I have only done this for the last two years but I know that wherever I am, I will make the time to venture back to the mitten to make the trip(came from MD this year). The food is phenomenal(everybody that cooks seems to be a gourmet chef!), the river is always fun, and the company is awesome(though I would be careful of passing out around the fire).
As for the river itself, who really cares in the middle of winter, just don't fall in! Seriously though, it seems to be a small manageable river that would be a legs on the deck summer trip. Dodging trees and avoiding rocks in the winter kinda makes your butt-hole pucker every once in a while and really puts the fun in it!
If you are lucky you end up in a camper or a hunting tent with a stove. Otherwise, tent city.
At this point in the year (winter) there isn't. Only cost is your meal for the group, pitching in for fire wood, and plow fees so you can get to the site!