My experience has been:
I tried the Linear app, but couldn't see anything more than a pretty landing page before an account was required. Next.
Replit. Wanted to get a feeling of how it works, but again, just a landing page and a button that says "Start creating" but instead it should say "Log in". Next.
OpenDream: "Create original art in seconds with AI". Cool -I say to myself-, let's create a couple of crazy pictures just for fun. Oh, well, these at least don't pretend to be fancy, the login prompt appears first thing right in your face. Next.
Replika. An AI companion, so curious. But the website's only purpose is to show a "Get the app" that brings me to Play Store. Wouldn't call it a webapp. So next, I guess?
Let's have some fun with some silly phrases in VoiceMaker! But after trying it out with "Casper, Male", I just wanted a second try with "Patricia, Female", and it already prompted me and didn't let me play anything any more. Bummer. Next.
Funnily enough, the best initial experience of these webapps, by a wide margin, has been Tower Game. It just does what it promises. It's a tower game. It runs straight out, and lets you play. No fuss. 10/10, best webapp of the ones I tested!
(PS.: PromptPerfect, "Your IDE for professional prompt engineering". Wow, it's crazy that we got to need such things, the world of LLMs is running too fast for me)