I have a similar problem.
I have a computer ruinning windows 7 64, I have Icloud 2.0 innstalled, and I have an Iphone 3gs and an Ipad 3 with sim all hooked up to the same apple id.
I have set up Icloud on all devices. Photos taken with iphone or ipad syncs perfectly to all units. But photos added to the upload folder within the picture stream folder on my computer won't sync. When I add a photo here it shows in "my photostream folder" on my computer, shortly after, but not on my iphone or ipad. (And yes, both I units are hooked up to wifi)
I have been messing with this issue for 3 days. And I am getting increasingly fed up. I have reinstalled the control panel for the computer several times, booted several times. Turned I cloud on and off on all devices, no change.
Tried to contact apple support, but they want to charge me 300NOK(50USD) for calling me. I didn't go through with that obviously.
If this isn't fixed I am seriously considering returning the new iphone 5 and the accessories I ordered last week.
If Icloud doesn't work, then Apple products really hasn't got the features I need.
I used to love Apple, but now, not so much.