Up to some point in my life, I didn't even consider using a trackball. I've always been using mice. But I saw a colleague of mine using it and I asked why and one of the responses was that it's always there, where you expect it to be. You don't move it around. And this keeps being the only reason I can justify using a trackball for normal users. By this I mean if the stuff you do doesn't require you to have these special kinds of controls. It's fine, but for everyday usage I don't see any benefits over a mouse. And after years of using Apple touchpads, I now see it as the most comfortable controller for work-related and casual things.

Some years ago I bought the Ploopy Mini Trackball. I ordered the assembled version to avoid any assembly headaches. And it was fine. The rollers weren't very smooth, but overall it worked fine.

Some time ago I saw this BTU mod. The most interesting part there was the bigger ball, because I felt like it could be bigger and it could improve the experience. And I found somebody who printed me the whole thing. I ordered some BTUs from AliExpress. And I also decided to give some paint love to my new build. And I also decided to get a full metal ball, to have a better inertia for swipes.

After finishing the build, I learnt some things:

• The smooth metal ball surface provides an extremely poor experience. Only after I thoroughly sanded it, it started to function properly. But then I faced another issue: for the metal ball, I bought metal BTUs. Made sense for me, so the ball doesn't wear out the plastic BTUs. And in combination with my sanded metal ball, this completely ruined precise movements, for example, when you need to click on some tiny thing. It almost felt like I was operating a ball-shaped polygon. It always tended to land slightly off. Annoying.
• The 3d printed parts are not precisely produced things. They can come out slightly different from the models. I had the top shell for the original ball as well, as I planned to have both BTU upgrades. And the original one appeared to be simply unusable. The BTUs made the ball positioned some millimeters higher than needed and the sensor simply didn't register the movements.
• Touchpad offers a really convenient way to scroll through long things simply by swiping away. I use this plodah's firmware to fix this. When I need to scroll a lot, I just need to use a toggle button.

In the end, I bought an ordinary new ball for the bigger socket and installed the plastic BTUs. And I can say that the experience now is much smoother. Not ideal, but I can live with it for now. Why do I even use trackball when I like touchpads more? I don't know. I just love experimenting and trying out stuff. And it looks cool.