I recon that I've plagued by many issues that others were not having here, but for me even the latest mobile build is really close to unusable.
I'm facing pretty much every issue you could name, the start menu stuck at loading, apps running very slowly, like they were running at a really low fps, everything resuming and loading and by that I mean, simply invoking the task view and going back to the opened app causes the app to resume, photos not syncing, heck most of the time the camera is even unable to save the picture, I take it, the thumbnail appears, but trying to open it crashes the app, and other apps can't open it too, but if I go to file explorer the picture is there but it's a 0 byte file, not to mention the constant crashing.
I'm not even using it on my daily driver, but I'm seriously considering reverting back to 8.1, because every time i need to use the phone it simply fails or takes a lot of time and retries to get something done.
Edit: Oh, and i already went through 3 hard resets on this build. The last one I didn't even restored the backup and start anew. But as soon as I went to install my apps the issues came back haunting me.