Now everything is present on all devices and they don't even take up a ton of storage: by default only the thumbnails are saved locally and then when you expand a photo you'll see a little cloud icon in the corner until it has a chance to download the full res version from iCloud.
The only downside I've noticed is that now that I have 25,000 photos on my iPhone, apps that want to access the camera roll take a few seconds to open the photo browser now (most noticeably in Instagram). To me that's a fair trade off, and, if possible, I'm sure most apps will release updates to make it faster.