Yeah, totally not necessary, Bob. It looks nice, and those retentive people (like me) will know that the inside of their subwoofer is pretty. Theoretically it allows smoother flow of air inside the sub, but I'm sure the difference is really negligible.
Well, I opted to not round over any cutouts. I don't think the air speed inside of the enclosure will start to give me any resonance. I think over time I will forgive myself or forget if I rounded them or not. I'm more concerned with the performance and outer look of the enclose. More emphasis on performance. More updates tomorrow on the Dual 10" thread.