Installed it yesterday and regretted it pretty quickly. My main bugbear is that it seems to have been dumbed-down, even compared to iPhoto. It feels like an iOS application that's been adapted to OS X - which indeed it is. The primary issue I have is that it's made it very difficult to organise my own photographs - something it tries to do for me, but fails. I used to organise all photos using Events. Events might have been an occasion (for example "Skiing Holiday Feb '15"), a work-related event (for example "Work Photos '15") and then everything else into chronological groups (for example "Oct - Mar '14"). This has all gone out of the window, effectively replaced by 'Years' > 'Collections' > 'Moments'. All well and good, except that I - the user - have no control over either how photographs are grouped in Moments / Collections or over how they're named. Take for example a day when I use my iPhone camera as well as my digital camera - I take a couple of photos in the morning, I drive somewhere and go for a long walk, then go somewhere for a meal and return home. 'Moments' will merrily split these photographs into several different groups, depending where I was and what device I used to take the photographs. In fact, even on a single walk, it may decide I've changed location sufficiently for it to be considered a different 'moment'. The bit that's really infuriating is that I don't have the ability to merge 'Moments' myself to rectify this - the assumption seems to be that the basic AI built into Photos is better than me at deciding how I want to organise my photographs. Well, it isn't. Similarly, I've also lost the ability to name an Event now that it's become a 'Moment' or a 'Collection' - rather than "Walk up Snowdon", I've got some generic name that may well be the number of the closest road or, worse still, a geographic description that's incorrect (I've already seen images relocated 20+ miles from where they were actually taken). It is, quite frankly, ridiculous that the user has no control of how photographs are organised in 'Moments' or 'Collections' - and to my mind makes the application essentially unusable with anything other than a handful of photographs (the library I imported has 7,500 photographs). Okay, I could use albums (and indeed all previous iPhoto Events are imported as albums). The problem here is that albums don't do the same thing as Events used to: - It's all too easy to overlook moving some images over from 'Moments' - There's no way of telling whether an image is in an album without checking that album - There's no way of simply listing 'orphaned' photographs - There's no way of moving images from one album to another Basically, Albums are merely a way of organising duplicates of selected images - they're not a means of organising the primary collection of images. The changes in the way that Photos handles the organisation of photographs moves away from allowing the user to organise images into Events and changes it to an arbitrary series of 'Moments' which can be illogical and do not allow user editing. Unless user editing of Moments and Collections (both naming and moving photographs) is introduced, I don't see how Photos can be used to organise a decent-sized library of photographs.