I absolutely love the new Photos, and the fact that I don't have to think about anything anymore, in terms of backup, syncing, etc. Once you release control, it's a huge weight off, and the photo philosophy makes sense. So many ways to search, and you can always manually make albums if needed- but I find the chronological concept and groupings pretty ideal.
The ONLY think I would wish for, and it's a very easy thing, is an option to change the stark white background to a grey or black. A simple slider would do, just like iPhoto, and I'd hope they will implement that before the final. Much, much easier on the eyes and makes the photos pop more.