Yes, I've seen this too, Steve--very cute! I've always had the impression they were looking through the window at me and were curious. If it was their reflection, wouldn't they attack it?
They are so curious about the world around them, and it's such a charming trait. No females for me, yet, but the little guy has been coming every day at 15 to 30 minute intervals. He's so much tamer than any of my other first hummingbirds have been. In past years it took at least a month for them to settle down and get comfortable with me prowling around, sticking cameras right against the window, working in the garden, etc. I figure he must have hatched here last year and was maybe one of the many juvie males I saw at my feeders and flowers.
I can't wait to see my first female and my first "U-dance." I would love to get that on video, but it would be tough to follow.