I'd like to know if the photos were uploaded yet, but an indicator isn't apparent. I'd like to know without resorting to checking a desktop/laptop. Is there one I'm missing?
It's quite easy to see indeed. If the two images match (left), all photos were uploaded to the Photo Stream. If they don't match (right), some pictures haven't uploaded yet.
NB: Photo Stream will only work over Wi-Fi, syncing only the latest 1,000 pictures taken in the last 30 days.
In the photos app, you should be able to compare between the "camera roll" and the "photo stream" in the albums tab.
The picture shouldn't appear in the local device's Photo Stream until it is uploaded.
To see this in action, go to the Albums tag. Take a screen shot. (Power + home) The photo will appear in the Camera Roll and (net willing will within a few seconds) then appear in the Photo Stream.