I’ve got a pair, they’ve been great so far.
I may have nerded out a little hard when I first got them, compared the to my SRAM AXS chainring PM, as well as some Rotor 2inpower cranks and Kickr. All was as you’d expect, lined up perfectly.
I got them for the same reason as you, to switch between bikes. Have moved them between gravel bike, rigid MTB and MTB dually without any fuss. Mainly just followed DC Rainmaker’s advice of doing a good hard sprint after installing them to get them to bed in, then do a calibration, and you’re ready to roll. (which I just do at the start of the first ride after swapping them)
Have clipped a few rocks with them, nothing really hard though, but they’ve just bounced off like any other SPD pedal I’ve used. No connectivity or data issues or anything so far afterward.
The only thing I’ve noticed is they don’t unclip quite as easily as regular SPDs. It’s not a spring tension thing, they’re just a little stickier? Nothing that’s going to cause you to call “TIMBER” when you stop at a set of lights, but noticable over SPDs.
They also have the option to put on a pair of SPD-SL bodies down the road if you want to make them a soley road pedal.
As for other options, the only other option I came across looking for the same thing was the Favero Assioma hack that GP Lama did. Everything else was crank or spider based as you said.
Thought about it, but the idea of having to modify shoes didn’t appeal as I also use my shoes for hike-a-bike when backpacking, and didn’t want to comprimise the sole.
So TLDR? I’d say buy 'em if you can.