Yeah the people at Apple don't seem to know how it all works either. I was on a support call to multiple "Senior Engineers" regarding issues I am having with it and the bets they could do was explain how it "should" be working and said that the way I am using is appears to be correct for now until Apple launch an app/site to allow us to view out iCloud photos on our PCs.
The way I use it is as follows:
Firstly I have the iCloud Photo Beta option enabled which allows me to take pictures on my iPhone or iPad which then appear on each of the two devices (not my laptop though). This uses the space I have paid for on my iCloud accounts.
In order to get photos into albums across my laptop, iPad and iPhone, I simply use the "Shared Albums" option within the iCloud Windows App. This allows me to store photos in albums which then appear on ALL my devices. This DOESN'T use the space I pay for in my iCloud account.
Finally, to get photos I take on either my iPad or iPhone to appear on my laptop, I just have the photostream option enabled on my phone which adds them to a shared folder on my laptop. This DOESN'T use space in my iCloud account but the fact I have the iCloud Photo Beta option enabled to get the photos onto my iPad or iPhone (depends which device I took the photos on) does use space in my iCloud account....Seeeee SIMPLE haha
Yeah I noticed that So yeah seems like this is the way to use it for now! Anyone know if I was encounter any issues such as limits on how long the photos will stay in the photo stream or has this been lifted now?