23-27 Miles each way depending on the route I take. I always do both directions on the same day, although I've come across many riders that will cover one direction with the bike one day, drive the other direction, and alternate the next day.
1. How many times per week? That's a tough one because I don't have to go into the office on a regular basis (mostly work from home). I've done it as many as five days in a week and as few as none. A five day week of commuting is good for the ego, but kind of hard on my body. 3-4 days at 40+ miles round trip is plenty for me. On days that I work from home, I typically take a recreational ride between 25-45 miles daily.
2. Recreational first? Commuting came first for me. I like to have a destination in mind, but working from home has forced me into recreational status most of the time.
3. How long? To the office is gross downhill with about 650' of total elevation gain and takes 80-85 minutes for the 23 mile route. Home is about 1500' of total elevation gain and takes 95-125 minutes (the wind also picks up in the afternoon).
4. Equipment? Depends on how much I'm carrying. If all I need is lunch and a change of clothes, my preference is the singlespeed listed in my sig. That's right, the SS is my bike of choice. It's a lot lighter (24lbs unlaiden), simpler, and is more nimble handling. It's got a basket mounted on top of the rear rack that is just big enough to hold a small backpack. If I'm carrying a larger load, expecting bad weather (wind), or want to ride the 27 mile route both directions, I ride the Gary Fisher listed in my sig (36lbs unlaiden). Gary is equiped with lights, rack, fenders, bell, computer, GPS, a folding basket on one side, and I use a panier on the other. I have different paniers for different loads/purposes. My road bike is my work from home commuter (18lbs fully dressed). It's not very good at carrying loads. All of my bikes are equiped with a tail light of some sort, pump, patch kit, multi-tool, and spare tube. I also always ride with a heart rate monitor. Gary is the only bike with a headlight.