My commute's about 16 miles each way with the short route, 19 if I take the scenic path along the river. The short route is a blend of multi-use paths and busy streets (although I avoid the busy streets in WA, as the drivers there are maniacal and don't ever seem to notice bikes). I hit 3 pretty decent hills along the way (including crossing the Glen Jackson bridge over the Columbia), but they just make the ride home that much more fun. Unless there's a headwind. It generally takes me about 1:10 to get in and 50 minutes to an hour to get home. With the short route, of course.

I bike in 2-3 times a week (working on keeping it closer to 3) out of 5.