Fast Replacement Improvements
A feature that isn't new but has been improved is the fast replacement of splitters and underground belts.
In the previous version, placing a belt on top of an underground or a splitter would automatically replace them. But if you're just dragging around a bunch of belt, more often than not you might accidentally replace a splitter you wanted to keep. I was very ambivalent about this feature, since I thought it was very useful in some circumstances, but I kept having these accidents where it didn't work as intended.
In the 0.17 version, this feature has been changed a little and I think it works really well now. It's similar to how your mouse-click "remembers" whether you're putting items in or out of an entity, for example when putting a bunch of coal in a furnace by just click and dragging a stack of it across several furnaces. Here, it makes sure you don't start grabbing items from them instead, once you run out of coal in your inventory.
The fast-replacement now works like this, too. If you just place a piece of transport belt on the ground and then drag it across the screen, you're in "belt placement mode". If you happen to pass an underground or splitter, it will not be affected! Here’s what happens if you drag a red belt across the two belt lanes:
You can still fast replace splitters and so on, if you explicitly click on them. Your mouse will also be in "fast replace mode" now, so if you drag your mouse across more belt and undergrounds etc. you will fast replace everything else.
With these changes, the fast replacement feature still works in cases where it is useful, but is also more convenient to use by not activating in cases where it is unwanted. Overall, a great improvement and I’m really happy with the fast replace feature now!