On my way in I usually take the direct routes (there are about 3 roughly equidistant options), but on my way home I like to to take the long way when I can. Lately that has been twice a week. Although the direct routes all take about the same amount of time, they vary a little from ~7 to ~7.5 miles. When I manage to leave 5 or 10 minutes early I like to take a longer (~8 miles) route in that takes me through Interlaken Park. This is a one mile road that I usually see less than 3 cars on (today there were none) and sometimes just a few cyclists and a couple of walker/joggers. It's a peacefull, hilly, wooded area, that is a nice respite from the traffic I've fought through to get to there.
My favorite long way home right now is along the waterfront, the trail through the railyards, and then along the Ship Canal. Going this way, rather than the direct route adds about 4 miles to my trip home, BUT this route gives me nearly 7 miles of uninterrupted cycling. This is even more of a draw than the views along the waterfront and through the industrial areas. It's more like a pleasure ride and not a commute to be able to ride for miles without stopping for a traffic light or stop sign!
I've been taking these longer routes as much as I can the past couple of months, because I'll be back in school next quarter and so probably won't have the time or energy to be taking the scenic routes. I'll be commuting 7 days a week, two days a week I'll be riding into town twice, so I'll be putting in 100-120 hilly, loaded miles a week, without a rest day for 10 weeks.
My pace is pretty mellow, although I will try and eke out burning a few more calories by speeding up if another cyclist appears in my rearview mirror!