Google Earth has much more complex features than Google Maps. More detail, different viewing angles and even the ability to view space. I'm looking forward to Google Earth but in truth, I can't imagine I'll use it anywhere near as much as Maps.
As for Flash, I'm surprised it wasn't released long ago. It sucks not being able to have that functionality on my Nexus. I've been a web designer for 15 years and not having Flash just seems ridiculous. I'm sure it's a developer thing...