Maybe it will expand in scope and usability as updates occur, but at this stage it is useless.
I don't find it useless at all. Then again, I'm not using it as my primary photo editor. It's not equivalent to Aperture or Lightroom.
HOWEVER, it's much better for viewing my photos wherever I am. And for sharing them.
First, for photos I take on my iPhone (and there are many), I have access to them wherever I am. This is super easy, and I have no importing to do at all.
Second, for DSLR pictures, I run those through Lightroom now. When I have my favorite photos, I generate JPEGs of them, and I import those into Photos. Then I immediately have access to those versions on all my Macs, and my iPhone and iPad. I can also share that out to my Apple TV for a slide show, and for others to view. It's a very convenient workflow for me, and it's way better than using the myriad Adobe solutions (what, have they taken like 9 cracks at Carousel now)?
If you want it to be an Aperture replacement, you'll be disappointed. It's a different product, with a different sort of strengths. For anybody who was previously using iPhoto (which is probably 10x the number of people who use Lightroom), it's a better product in every single way.