I've been using Google Fi for years and generally have been very happy with it. At one point it was also advantageous because data was charged at a flat rate of $10 per MB worldwide, and because we didn't use too much data it worked out less than what we had before (Verizon) in most months, both when we travelled and when we didn't. However, now that the kid is in college, data use has skyrocketed and the "unlimited" plan is more cost effective. The problem is that the new plan excludes international coverage, and so if/when we travel abroad we have to switch the plan over to the per-MB plan, then remember to switch back before the month ends.
So I'd say whether Google Fi is right for you really depends on your domestic data usage. If it's low, it's great. If not, T Mobile or another carrier may have better options. I haven't looked into them so I'm not sure. (I will say that having used Google Fi in probably more than 20 countries, it has worked almost flawlessly. It's so great to turn on your phone after landing and have it just work, no worries about SIM cards or anything. There was exactly one problem in the last 8 or 10 years: in Greece, the network kept defaulting to lower speeds in some areas. My Android phone was affected, but an iPhone on the same plan was not, ironically.)