Is there a huge difference between 720p or 1080p HDTV?

[Biroutman]

I got a 720p beamer and i'm sitting roughly 3 meters away which is close but i still cannot see the pixels (as it was the case with my previous sd beamer), the picture is really very smooth (screen is 1.8 meter wide) to me 720p is enough even for a rather large screen.