Besides the joy of watching construction dones, and besides sharing ideas, Dyson Sphere Program's blueprints are also nice for building cleaner factories.
Oil refining in Dyson Sphere Program is slightly ugly. Oil refineries are more annoying to tile than assemblers or furnaces. With assemblers and furnaces, I can easily slap them down one next to another and connect them up, inputs on one side and outputs on the other, and it's fine. One machine, two belts, two sorters, easy. They tile amazingly well. But refineries need a little more work to make them tile.
This is where blueprints are nice. Yesterday I designed an oil refinery block that tiles just as nicely as an assembler. It's not just one refinery, it's two, and it's more spread out, but it tile. It feeds input from one belt in the back just like an ordinary assembler. It feeds out into two output belts running horizontally. I can drop down one of these blueprints for each oil-second of input I need to process and it'll run right away.
This makes it easier to keep the factory clean. It takes a well-defined amount of space and processes a well-defined number of inputs into a well-defined number of outputs. All that makes it easier to plan the factory and make sure I have enough space for everything. The early-game part of my factory is a mess of criss-crossing belts. Everything crosses everything else because I didn't know what buildings I would need or have or how much space they would take. The part I just built, which is for building structural matrices and only structural matrices, is much cleaner, because I knew how much of everything I needed and I found a nice big empty space to build it in. I knew how much I needed because I set a target (60 structural matrices/min) and I calculated how many of each machine I need to hit that production target. This cleaner layout is a nice benefit of building with a plan and using blueprints.