Going to chime in with my $0.02 since everyone seems to be having a bad time with it. Besides the initial upload, which I was lucky enough to do a 30gb upload on my Uni net (Google Fiber in AUS!), it's been good for keeping all my personal photos.
Once it was uploaded I updated my iPad Air and iPhone 5 to the 8.3 betas and switched on iCloud Photo Library and selected optimise for the iPhone and full res for the iPad (16gb and 128gb respectively). Also turned off Photostream.
What I've enjoyed so far is being able to go through my entire library and deleted/edit my photo's and then have the update automatically on my other devices without having to plug in and sync. For example when I'm out or chilling I can edit and view ANY photo on my iPhone from a 30gb library on a 16gb device. The editing is simple, yes, but I usually only want to change lighting and colouring a bit anyway.
What I haven't liked or want Apple to implement, is a GOD DAMN GEOTAG. I've sacrificed enough giving up my iPhoto Events/Albums for the "Moments" view, which I guess is ok if your photos all have the proper metadata, but if they don't I at least want to be able to add or change it. Also I hope they have made it so iCloud doesn't upload on your mobile data, because there is no setting I can find for that. They also need to add a Faces view, and in relation to changing metadata/organising, they need to make it so you can do it on mobile & mac, so then we can slowly sort out our libraries on our mobiles when we get spare time anywhere.
Overall I'm happy though and like it, I'm putting faith in that my photos are secure both privately (2 factor authentication, strong passwords, Apple protect me pls) and safely so that I don't need too worry to much about my backups, although I do keep multiple. I'd say it's more for personal use for consumers, because unless you have an awesome internet connection most of the time, uploading multiple large JPEGs or RAWs from a shoot will take forever and possibly lag your net. So I'd probably look at something like Adobe Lightroom for managing photoshoot collections and maybe just put the ones you like into Photos. As I said, I feel it's more for simple personal use anyway.