I use Flickr, and turn Photo Streams off because I don't want them wasting my iPhone's storage.
It's dumb how they work, IMO.
If you're not careful, you can quickly fill your device or delete something forever.
Ideally, Apple's service should work like iTunes Match.
OTOH, Flickr offers 1TB of free and permanent storage that lives completely separate from my iPhone.
When I'm done taking a bunch of photos (like today) I'll transfer them to my mac, organize and edit them in Aperture, upload the ones I want to Flickr, and delete them all from my iPhone so I'm ready to go again. It's the same process I've always followed with digital cameras.