I'll second the recommendation to swap the stock suspension fork for something rigid. I commuted on a 2003 Hardrock (basically the same bike as above just much smaller) for about 4 years before moving on to something lighter. I added a Surly 1x1 rigid fork, Planet Bike Freddy fenders, an Old Man Mountain rear rack, and slick tires for the three warmer seasons. I still use the bike in winter whenever there is the threat of or actual snow/ice on the roads with Nokian Mount and Ground WS160 tires.

When I was commuting year round on the bike I swapped out the stock MTB crankset for a 48/38/28 to give me more top end gearing. I'm back to using the stock crankset now as I often need the low gearing to get up some steep hills in the snow.

Additionally, I cut the stock handlebars to make them about 2" more narrow. This made a huge improvement in comfort for me especially when using bar ends.