It's one of the few alternative UIs for Lemmy that includes moderation features, so that makes it interesting as a replacement for the default Lemmy-UI.
Right now it is still early days and Photon is very actively developed, so don't expect a perfectly polished experience. Once it stabilizes, there is a chance we will switch over to it as the main UI for Slrpnk though, as the current official Lemmy-UI is not very actively maintained any more with the main developer working on a re-write.
Update: Linked in the sidebar now. Will probably take a few more weeks/months before it can be used as a full replacement of the lemmy-ui though. Looking very nice overall though.
After messing around with it for 30 minutes, I think I can safely say I prefer Photon to the default UI. I especially like the addition of being able to moderate posts without having to actually go to that post's page first.
The only thing I miss from the old UI are the themes, as I find the dark theme to be a bit too dark, and a bit lacking when it comes to distinguishing separations between UI elements, since everything is the same color. But I'm sure more themes will come in time.
Really enjoying seeing how nicely the lemmy ecosystem is growing and becoming more polished. with the new Eternity app for lemmy and now Photon, I lack for nothing.