I’ve used a trackpad as my primary pointing device on my desktop Mac (or laptop connected to an external display) for many years. I used the original Magic Trackpad for most of that period, then upgraded to a Magic Trackpad 2 along with my new iMac a couple of years ago.
I don’t make use of the Force Touch features in the Magic Trackpad 2 very often. I have a couple of things set up in Better Touch Tool, but don’t really do that much with them. For me, the two advantages over the original Magic Trackpad are the larger area and the internal battery. The larger area is useful, particularly since I’m using it with an iMac with two external monitors, so I’m moving my mouse pointer side to side quite a bit. The ability to charge it via Lightning rather than periodically replacing batteries is nice.
Is either of these things worth $129? Maybe, maybe not. I’ve still got a couple of 1st generation Magic Trackpads that I use with other computers that I haven’t upgraded yet, so the evidence suggests that I don’t value the benefits of the newer model that much. That said, if I were getting a new Mac that comes with a pointing device I’d certainly shell out $50 to make it a Magic Trackpad 2 rather than a mouse.