It does back up all your photos to your computer.
Yes on YOUR computer, this ISN'T a cloud storage service. And what if you do not have a computer and shoot more than 1000 photos? Then your photos only live on your idevice as they do today. And if you have a digital camera, this service is 100% useless unless you want to sync your camera with your ipad and then to icloud and then to your computer, assuming you have one.
No one has been able to tell me the REAL value of this service other than the ability to shoot a pic with my i device and have it sent to any other i device or Mac in my sync ring, which is no better or easier than what we have today, save for the fact that you do not need to remember to click "share" in your photos on your i device. In fact it is worse, because now my one picture will eat up memory and or HDD space on multiple devices instead of on my Mac and in the cloud at MM where it makes sense. Today if my Mac crashes I know all my pics are safe and backed up on MM and in Time Machine (okay I have another back up as well) in the future with icloud that additional saftey net is gone. Of course I have another redundancy over Time Machine, but still, MM was a nice comfortable back up place that was 100% off site.
And again, if you do most of your picture taking with a camera, and if you want to make more than the last 30 days or 1000 photos available to other users, in your sync ring or not, this service is useless.
Not only that, my 10 year old shoots all sorts of crap with his ipod, I do not want them on my Mac, nor my wife on her ipad nor on my iphone, but he may want them on his Macbook, but some pics maybe I DO want. Not sure how THAT will work, so far it sounds like all or nothing.
AFAIK most people share tons of pictures with tons of people, from tons of different periods of time and have been doing so for years and years. Apple somehow IMHO doesn't think this will continue or doesn't want to be apart of that. I guess they feel Twitter and Facebook have taking over the world for this type of sharing and have bowed out.