My product photography improved somewhat because by using long exposure on a DSLR I could make up for my lack of proper lighting gear, but I was still limited by windows as a natural light source. I later picked up a pair of 600 watt quarts-halogen video lights, which look great for video, but run very hot and have $15 bulbs that are delicate and don’t last long. Also, having only 2 lights causes an endless battle with shadows, especially shooting inorganic objects.
Finally, as you see in this video, my current setup consists of 4 Canon 430EXII flashes I picked up, one by one, from craigslist, a canon flash controller, several bodies, and a range of lenses I’ve accumulated over the years. The flash controller uses infrared to trigger the wireless flashes. Having 4 lights makes reducing shadows easier, but not perfect. And depending on the size of the object I’m shooting, which usually is large and has many flat, shiny surfaces, it seems you can never have enough light!