Just something I figured out this morning. I experimented with photo stream between a 1st Gen 64gig WiFi iPad and my iPhone 4. I took a couple stupid pictures and sure enough, Photo Stream worked great. On the iPad, I saved the "good" pictures and then turned Photo Stream off on the iPad. This effectively deleted all the Photo Stream photos that I didn't save on the iPad. It worked the same on my Macbook Pro. Turning on Photo Stream re-downloads the photos from iCloud. So I'll have to go into iCloud and reset my photo stream. All the other solutions were to go into iCloud directly and reset the photo stream. Not sure if this will help anyone, but it provided an easy way to delete Photo Stream photos off a device instantly.