Here's a bad photo of my commuter:


I commute 3x week (22-24 miles/day) with 10-15 pounds of "stuff." Part of my route includes dirt roads/trails, which it handles just fine (as long as it's not too muddy). The bike is no lightweight (30 pounds), but that's because it's equipped with fenders, dynohub lighting, front low-riders (stainless steel), and very sturdy wheels (36h rear). I tend to think of it as a car replacement.

When I want to go "fast" (in quotes because it's all relative), I have another bike that doesn't have fenders, racks, or lighting.