When you take a picture using your iPhone, the picture will use the iCloud canal to share those pictures on all your devices sharing the same iCloud user name with your iPhone iCloud user name, now like you have noticed it on your iPad, your pictures get downloaded to your camera roll moments after you take the pictures, that should be the same if you were having a MacBook, the pictures will be download to an application called iPhoto in your MacBook. But since there is no such a version of that software for windows, and that there is no present software managing iCloud photos on your windows, you are not able to see those pictures. Your pictures are in the iCloud all the time until you delete them from one of the devices having those iCloud pictures, saying so i do not mean that your pictures are in the iCloud where you can open iCloud on internet and see them just the way you can see your iCloud calendars, mails, contacts, iWorks. No your pictures are in the iCloud but only visible on iDevices or on Mac computers sharing the same iCloud account with your iPhone iCloud account.
I do hope that Apple will release a software which will allow windows computer users to automatically fetch their iCloud pictures on their computer. If in the near future you own a Mac Computer and with the latest OS X, then you will find iPhoto in the application, just sing in your iCloud account and voila.
