Regarding photos, I posted a link to a very detailed article about it in another thread. Here it is again: http://www.macnn.com/articles/15/02...for.iphoto.users.falls.short.on.pro.features/
In my own experimentation with it, there's a few things that are missing that annoy me. However, at least half of them I expect to have put back in by the time the final one arrives. two of the biggest missing features for me are the quick preview (we can quickly compare your added to the original), and flags.
The speed, the organization, the handling of raw files, and the speed – did I mention the speed? — are impressive. I also like the editing controls, they seem a definite step up from iPhoto, but they will not impress any professionals. On the other hand, they aren't meant to.
One thing that is annoying me is that when you are offered a chance to use the iCloud Photo Library, it's an all-or-nothing situation. You either have to import your entire photo library to iCloud, or not use that feature at all. It should be more savvy about that. I feel like I need to reiterate for the paranoid among us that the iCloud Photo Library option is exactly that — an option. You don't have to use it.
Photos, at present, and it is early days yet – feels like about two thirds of a program. I expect they will get it closer to 90% of a real program by the time the initial release happens, which I expect to come along in April or May.
Bottom line: as a consumer photo management and editing program, Photos is well on its way to being a superior alternative to iPhoto. A few restored features, and a little spit polish, is probably all it needs to be a first class replacement.