This site Bugs Apple Loves might be a little unfair, but the iCloud photos part is good:

You took some photos. iCloud says ‘Uploading 847 items’. You wait. Next day: ‘Uploading 847 items’. Week later: ‘Uploading 847 items’. Is it stuck? Is it working? Is there an error? There’s no progress bar. No ETA.

In my experience, Apple tries to optimize when it syncs based on battery life or network or some other hidden criteria. In practice this just makes photo sync slow and unreliable.

@manton Especially frustrating if you really need it to sync quickly for some reason. More than once, I have had to Airdrop between my own devices because I couldn't convince it to sync right away.

@manton I find that so frustrating. I absolutely want a button that says: just get on and sync now without delay!

@sharding @manton Literally every time I look, photo syncing is paused for some reason. Battery, network, vibes, weather.

@Miraz Me too! After I take a photo, I really want it to sync to my Mac or wherever right away.

@sharding Yep, a few times recently I’ve given up waiting and just used AirDrop too.

@manton Sometimes I’ve ended up manually transferring the photo from phone to Mac as a way of shortcutting the process so I can get on and use it in a blog post or whatever.

@Miraz same here. Sometimes the photo pops up on my iPad or Mac right away. Sometimes it doesn’t. I just default to manually sending it every time now

@miguelmanalo For me it just depends how long I’m willing to wait. It’s so erratic!

@manton I just sync to my own NAS for photos and video playback. No need to worry about paying for another subscription 👌🏻

@manton I agree. Apple syncs quickly when the device is charging and on wifi. If you are out and about, try charging the phone AND using a portable wifi device to get photos to sync faster.

@manton also their servers are garbage, the bandwidth is ridiculously low. It’s some of the most expensive storage in the industry with the absolute worst performance.

@manton Recently I needed to upload a 12GB file and it kept failing, so I split it in 10MB chunks. 2 weeks later I arrived home and transferred the file locally. I then couldn’t use iCloud for anything (even apps that use cloudkit for settings) for a month, before it managed to delete all the chunks. I am lucky that it eventually recovered, I thought my whole account was to scrap. There was nothing I could do, basically every one of my devices lost access for a month.