I ride my cyclocross bike to work, typically at least one day per week on average, year round. In the summer I try to do Tuesday and Thursdays and in the winter I tend to just read the weather. I run fenders on it most of the time, but from Sept to Dec since I race it on weekends I go without them. But I'll get lazy and skip a rainy, cold day or very, very cold days. I have several light options, between this and night MTB racing. I prefer a 3Wish LED, bright enough without blinding anyone. I use a Niterider Mi-Newt USB on my helmet.
I spent around $1000 building it in 1999, so it's paid for itself many times over. I run high volume, small knobby cross tires most of the time, although lately I've been using road tires because it's been dry on the pavement and wet on dirt. I typically mix it up, Highland Canal, some of BMX trails, pavement, streets. Depending on route it might be 12 to 14 miles for me and it takes about 45 minutes to an hour. There are showers at work, which is nice.
I'd put you on a 58cm bike, although my CX is a 59cm and it works fine for commuting. You might prefer something taller, like a 59cm or 60cm, but that's hard to say without trying. Mine is a bit tall for CX racing and a little long. I'm 6'0" & 34" inseam and I prefer long top tubes so it works. My guess is a 57cm would be too small for you.
I'm split on single speed for commuting. If you're using the train or bus, they are nice for simplicity but for 10 miles into a head wind or trying to keep up with traffic, no thanks. Call me anti-hipster, but I love gears.
BTW, I have an old GT MTB that I'm selling. I have it on CL for $200. It would make a good starting point for a commuter, LMK if you're interested and we can work out a deal. It's not heavy, that's for sure. Drop bars and 1.9 tires and you gotcha a monster cross bike.
Personally, from a strictly economic sense I think you have to factor in gas, wear on your truck, wear on the bike (chains, tires, lube). It's tough to totally justify unless you ride a lot. But when you figure you burn calories and burn off stress, the health benefits are very much worth it. Maybe it's too hippie to mention, but it seems such a waste to drive around a truck with just me. I'm a nobody, so I have the time.