Smart Compose is a godsend for me. I write a lot of business emails using Gmail, the ones where you have to be perhaps unnecessarily polite. I find myself writing the same things over and over again. You may wonder why I don't use something like tex texpander and the answer is that I do but it's not suited for those kind of short phrases that simply add politeness to a message (at least not in my opinion.) When smart compose suggests a phrase, I do of course need a few milliseconds to decide if I should press tab or skip. But that doesn't slow me down at all because it saves many seconds and it only sets me back a few milliseconds. But the most important thing for me is that I don't feel like a robot typing the same things over and over again, I feel like it's helping me protect my sanity at work.