After just a day of playing with it, I love the Google Photos service for what it is, but I was pretty sure it wouldn't be a viable backup solution. If a service offers anything more than strictly "file backup", it's a sure thing you will lose quality and/or won't be able to get at it easily. I already have a good backup system utilizing my free $50/month Azure benefits that come with my MSDN subscription so I'm not really concerned about it. I personally don't care much about sharing features but if Google can actually make this a good backup + sharing system then they will win. For me "good" means my original files are kept as-is and that upload/download is relatively quick. I'm fine with days, not weeks. Azure (CloudBerry) took less than 5 hours for my 100GB library over 35Mbs upload FiOS, but Google Photos isn't even 1/10th of the way done after a day.
I love how it has mashed-up my photos into categories, stories, animations and collages. Literally love it, it IS great. But backup system, it is not.
It's not super automatic but CloudBerry Explorer for Azure [1] is free and has a pretty good folder sync feature. I basically just keep all my photos and videos in single a folder on my desktop. Whenever I copy my families phones or tablets to my PC I just run the saved sync, it's usually pretty quick. I have over 90 GB of stuff so it actually took a long time for CloudBerry to analyse the folder for the first time, after that it figures out what's new and needs to sync pretty fast.
I love how it has mashed-up my photos into categories, stories, animations and collages. Literally love it, it IS great. But backup system, it is not.