I've been very happy with Fi, after having used Verizon, T-Mobile, AT&T, and Sprint. But I'm also not dead set on them.
I don't really need anything faster than 10 or 20 Mbps anyway, and the Fi app and support team are super easy to work with, which is more important to me than super fast speed or priority. It looks like the reddit person was trying to use it as a permanent international plan, which isn't really what it's for. I do like being able to seamlessly and cheaply use my same plan when traveling for a few weeks though.
If Google ever sunsets Fi, that's fine, I'll just move to another carrier then. Doesn't seem like an urgent situation to me?
But if there are any better choices for about $80 to $110/mo for two lines, I'd be all ears! T-mobile seems more expensive, but if they have significantly better speeds and international roaming at the same price, that'd be worth considering?
If I remember right though, their customer service was horrible. That was a long time ago though. I'd much prefer a slower service with good support than a faster one with automatic or outsourced support.