I’ve had very little time with Photos but my general impression is that it hits a sweet spot for the casual-to-enthusiastic iOS and digital camera shooter. Its navigation is more nimble and, from what I can tell, its performance is significantly improved over iPhoto’s, which I found sluggish with large image libraries. And, scaling back to the big picture, it’s the first of the old iLife apps that shares a common experience among the Mac, iOS devices, and iCloud. All your photos, your most recent edits, wherever you are. It’s an app worth looking forward to.
It seems that The Verge and Christina Bonnington at Wired also got some hands-on time with the software. General consensus seems to be that it’s a lot speedier than iPhoto—which, let’s admit it, wasn’t a very high bar—and is, also unsurprisingly, heavily influenced by the iOS Photos app.
Developers can get their hands on Photos as part of the OS X 10.10.3 beta seed going up today; everybody else will have to wait until that update is publicly released later this spring.