Bonnie Cha, Re/code:
Before today’s beta release, Apple gave me the opportunity to have some brief hands-on time with the app — not nearly enough time to do a thorough review, but enough to gather these early impressions.
Apple had previously said that Photos would be available in early 2015. Now Apple is saying this spring. I assume this is welcome news for the 'Apple needs to slow down' crowd (for the record, I'm not part of that crowd).
From what I've seen, Photos along with companion iCloud Photo Library is looking good. As much as I have enjoyed iPhoto over the years, it simply wasn't made for today's mobile world.
Related: Apple had updated its Photos preview page.