I have found the editing tools in Photos to be very basic, and almost identical to their iOS app.
Admittedly I don't edit a lot of photos but I found the controls to be reasonably complete:
http://imgur.com/A8vITod
What is missing that iPhoto had?
I really don't like their "less is more" approach to everything they have been producing. Some areas have seen improvements, but there have been a lot of features taken away.
Like I said, my guess is that Photos is going to be getting more frequent updates to add new features, just like FCPX did.
I did a brief google, and found a big issue is the ability to hide pictures in the new Photos app. Apparently hidden pictures are moved to a new album for all to see. I haven't used this, but for someone that doesn't want their kids looking at pictures not appropriate, it would be a major issue.
Personally I would use an entirely different library for this use-case.
I know at the moment it is optional, but this drive towards the use of iCloud is also annoying.
On the other hand for people like my parents this is a fantastic feature. Gone are the days when I have to worry if they are using their Time Machine drive to properly back things up.