I’ve used Stan’s sealant for a while. I honestly can’t attest to its effectiveness, though. I haven’t had a flat that I can remember in over a year. I usually remember those things.
I’ve had good luck with the Nimbus in 35 so far. Zero flats. I did have a manufacturing deflect in one, and I had to limp home with a bulge in the tire, but it didn’t go flat, and Specialized customer service replaced it with no charge or delay.