Nice to see Preact catching up on some features in React proper... I stopped even trying to target Preact a little over a year ago for a couple reasons. First is missing features in React that are very useful, this is a large bridge. The second is that React has *REALLY* helpful tooling in terms of diagnostic messages in the console as well as browser extensions themselves.
Beyond this, the extra 60k or so that React has in payload over Preact + compat isn't that much in relation to an application's payload, and the performance difference is negligible in most real world cases (in my experience), so I've favored the better tooling and diagnostics.
That said, I do love to see smaller frameworks as they are an incredible option for bandwidth and resource limited devices or when using a progressive enhancement.