This move from Amazon sparked me to revisit the cloud storage options out there and ended up with Google Drive. As a longtime Dropbox user, I've always used them and never looked at other options because of their awesome desktop client, but they are really dropping the ball when it comes to competitive pricing. So I'm happy to say after installing the Google Drive desktop client, it is pretty much on par with Dropbox, and both are way ahead of Box, which is slow and buggy.
Some of my findings...
Dropbox
2gb - free (can get up to about 5-7gb free if you do a bunch of stuff)
1tb - $10/month
Cons: No 100gb pricing option.
Google Drive
15gb - free
100gb - $2/month
Cons: No camera upload, though I bet this will be changing very very soon.
One Drive
15gb - free
100gb - $2/month
Cons: MS have the right to snoop your files for shady content. Have a policy against storing files with nudity, pirated stuff, etc.
Box
10gb - free (50gb free if you downloaded the iOS app during the promo period)
100gb - $5/month
Cons: 250mb file size limit unless you pay. Buggy desktop client.
iCloud
5gb - free
20gb - $1/month
200gb - $4/month
Cons: Only works with Apple products. No 100gb option.
Amazon Cloud Storage
Unlimited photos/5gb everything else - $1/month
Unlimited everything - $5/month
Cons: no auto syncing from what I'm reading. Archaic drag-and-drop to upload.