May have made some headway. After uninstalling, reinstalling, etc. with no improvement. I tried syncing manually via iTunes, and everything but Photostream would sync just fine. So when I tried to sync Photos only via iTunes, it kept wanting to go to an old Blackberry Photos folder, and also told me that there were no photos in my Photostream folder. After awhile, I opened the Blackberry Photos folder and there sat a duplicate set of Photostream Cache folders that appeared to be identical to the cache folders in my Photostream folder.
I deleted the cache folders in the Blackberry folder, then deleted the Blackberry photos folder (moving any photos I wanted to keep into my Photostream upload folder). By then, I had about given up on Photostream and went off to do something else. A couple hours later, I looked at my iPad, laptop, and iPhone Photostream and voila, everything on my iPad and iPhone was synced-up. Everything synced except 2 photos, both panoramas that I shot on my iPhone, those 2 panos don't show up on any device. Not sure why, file size max on Photostream?
Now, the Photostream folder on my laptop shows the "Blackberry" photos I added to the upload folder ok, it still doesn't show any of my iPhone photos shot in the last week or so.
I just tried manually syncing Photostream with my iPhone and when I try to select the Photostream folder I get a dialog fault that says invalid selection or folder. Tried iPad and I can sync only computer to iPad.
I have also re-set password, etc to try and see if that was an issue. Has not appeared to make a difference.
I just think the switch to iOS6 + windows = some major issues at Apple.