I think you’re comparing apples to oranges - the U1 is not intended to be a 3-in-1 ever - at least that’s what I would infer. It is just a 3D-printer, and as such mechanically very different from the 3-in-1 like SM2 or Artisan. It may become a 2-in-1, because the mechanics should be able to carry a laser, but CNC milling would most likely ruin the machine.
So, I consider the U1 more an expansion of the offerings of Snapmaker, and the toolchanger paired with CoreXY is a nice thing - I like the concept. I followed closely the Prusa XL, which is basically the same concept, just larger. If you’re really into multi color/multi material printing, these type of machines would be a good choice. The single-printhead filament switchers (like Bambu) waste a lot of material. A big question for me would be: Is it as hassle-free as the competitors? This remains to be seen. I personally think the huge selling point for the Bambu- and Prusa-Machines is simply: They work, reliably, out of the box, no tinkering, no calibrating. Which is a combination of good mechanics, tons of sensors, good firmware and good software with dialed in profiles. And I guess any competitor that does not match these standards, will not be successful in the long run. Snapmaker has not the best history in that regard… But companies may improve, we’ll see.
When you say the linear modules are slow - yes, they are, always have been. The Snapmaker 2 can do the three workloads it features, but all of them rather slow. 3D printing needs to shove around considerable masses (the backside of the all-metal-concept), and this cannot be fast, at least not without excellent vibration and backlash compensation in software. Milling is limited by the after all not so rigid structure - if you go too fast, everything flexes and you loose dimensional accuracy. And 200W is not the most powerfull spindle, limiting feed rates and cutting depths. Laser again is limited by the heavy weights that need moving around. So whatever modules Snapmaker may or may not come around the corner: These limitations will remain. With the Artisan they learned and improved, but some limits apply there also - I would be surprised if they ever are able to shove around the 3DP head with 500 mm/s or something near with good results.
IMHO, SM2, and also Artisan, are mainly hobbyist machines - if you expect more, you most likely will be disappointed.
After my long monologue: What is it you would expect from Snapmaker to come up with to grant them that they delivered on the promise you think they made? What module(s) and/or addons would that be?