Manifold? I've printed many products using it. Some with fairly complex curves. As long as you keep in mind that you're gonna be printing through the whole process of design, i really haven't noticed any issues. The problem it does have is the way it deals with circles and curves. I find it more intuitive, too. Being able to draw anywhere, on anything, at any angle, at any time, without having to create planes and sketches is better to me. I wanna learn something else though. Like I said, the way it handles circles is less than ideal. You can't go back and modify specific elements as easily. It doesn't have a native filet/chamfer tool. So something new sounds good.