Why doesn't Google Photos work for you ? It does provide all the features you mention (depending on definition of "Nice gallery feature" of course), and on top of it really awesome search features.
Full disclosure: I work at Google (not on the Photos product though). All opinions expressed are purely mine, and not of my employer.
Google just shut down Picassa and you expect people to trust Google again and move to Google Photo ? Google should build trust first and foremost. Anybody who would still rely on a "non core Google product" at that time risks nothing short of a big disappointment.
Api,services are being shut down and this time people don't even have 2 months to move. Picassa and Google Photos are 2 different products, if people stuck with Picassa there must have been a reason.
I agree with sergiotapia about Google Photos falling short in the area of sharing pictures among family members. If we do trust Google not to kill off Google Photos...
Without grahamburger's hack of creating an independent, shared account (which I wonder whether is strictly allowed by account usage terms), how can a family share all of their photos? I'm not talking about sharing an album. My wife and I would like all photos taken from either of our phones be automatically uploaded and shared between us. We've not found a way to do that using Google Photos without making everything public, which is unacceptable.
Full disclosure: I work at Google (not on the Photos product though). All opinions expressed are purely mine, and not of my employer.