The Chrome extension is now live: https://chromewebstore.google.com/detail/pdkkoohhhodjoidmefi...
I went with an extension rather than trying to recreate the full experience in a conventional web app because a lot of Serendipity's desktop behaviour benefits from being persistent while you're actually browsing the destination sites - Surf, feedback, saves, Similar, etc. - rather than making you bounce back to a central webpage or putting sites inside an iframe.
I'm also working on a very lightweight zero-install web trial so people can experience a few Surfs before installing anything.
Thanks particularly to the people here who pushed on the installation friction. Would be interested to know how the extension feels compared with what you had in mind.