I've got a Simagic Alpha with their GT4 and GT1 rims. Not from NA but I bought mine from sim-motion EU.
Haven't had anything break yet so can't say much about how replacements work.
Ordered somewhere in December when the website said they would arrive in January and got them mid March. Needless to say, not the fastest shipping after a few shipping and customs delays.
The Simmotion support replied to my mails really quickly (usually within 15mins), so it's not like they were the issue.
Just takes some time for the products to get shipped across the globe. Would expect something similar if you need a replacement when the distributor needs parts from Simagic.
Wouldn't worry about sim-motion as a distributor if their EU branch is anything to go by.
Only other negative thing I have to say is the software (getting FFB to work), it's not plug&play like it is with Logitech or Fanatec.
This is a great list for compatibility. Not a major issue in the games I play, but a hurdle nonetheless.
Other than that, happy with the Alpha and the GT1/4 rims. Wheelbase and rims are solid.
The D1 spec QR is amazing. I can swap rims quickly in VR without taking the headset of and there is no need to worry about fragile pins
FFB is great once you dialed it in (but thats my first DD, so thats not saying much).
Another story if the Alpha Mini is worth its asking price, but the Alpha and their rims are solid products.