Only single player.
I started a new single player world when the 1.14 snapshots started coming out, and play only in the snapshots on that world (tad challenging when dealing with various bugs). After the release of 19w02a, I started having several issues in the world, most notably not being able to depend on the Elytra to work. I have noticed the server ping as high as 55ms and typically never gets below 35ms (prior to this snapshot however, never really went above 35ms).
Same issue in 18w48a
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As an admin on a popular vanilla minecraft server, spectator was our easiest disguise. It wasnt perfect, sure, but now it's basically useless for what we use it the most for. All you've done by changing it is give the cheaters an advantage. The only people that would of requested spectators be easier to identify are the cheaters themselves, the rest of us would rather be completely invisible. I'd say just give us the choice on if we want spectators to be easily identified or not, even if all we can do is switch back to the slightly transparent version.