Sorry but I have exactly the same issue than Eugenienatchez... : it STOPPED working... meaning, it used to work perfectly.
Without any reasons since several weeks, all my shared photo streams disapeared from iPhoto (but Ok in iOS devices)...
I tried to activate (once again) the checkbox in the preferences panel of iPhoto, the box refused to be checked...
In the preferences panel of OSX, acount login is OK, iPhoto check box is OK as well in this same panel...
Unbelievable... and once again, it worked perfectly well, so far...
My photo stream used to work (mostly) perfectly until I updated to iOS7. Since then, the photos don't appear on my PC. The photo stream folder in my Photos app still fills with photos as if they were transferring, but they never appear on my PC. I've tried turning it off and on again (haha) several times, and I even had to factory reset and restore my phone (laptop died while I was updating it, sigh). Still nothing. I'm using an iPhone 4, which was always fine until iOS7.
Same thing here. Works when it wants to work and then only picks random photos not all of them! I thought I solved it by deleting and redownloading Icloud but only worked for a few days then back to haywire again.
This is an ongoing problem and no one seems to know why or what to do for sure!
I did what one of the forums said- go to settings, my photo stream, turn it OFF and then turn ON again. that worked great for a few days, then today I had issue and tried doing all this again, NO Luck!
this is crazy
the only solution is to get the stupid wire out and hook ipod touch 5G to my windows PC and manually put the photos in. what a pain