Ok, well it's only one night and all, but...
If I left my iPhone 2.0.x unplugged overnight I would have between 50 and 60% charge left the next morning, even if I used EDGE. After upgrading at about 7 pm last night, I charged it and left it unplugged. It had a 100% charge this morning. I have everything on except push, and I am using 3G (the upgrade turned this on).
My guess is that the changes to the power handing have to do with idle time loading. That is, the phone is not spending as much power as it used to when it's "turned off" in idle mode. This would explain my much better battery life, as well as other reports by heavy users that there is no difference in their battery life.
As others have reported, 3G speeds have dramatically improved. I'm on Fido in Toronto and used to consistently get about 1.1 Mbps using testmyiphone. Now I get over 2 Mbps every single time.
Reception is absolutely better than it was. I now get a full set of 3G bars in my house, whereas I used to get 2 or 3. Before anyone tells me Apple just changed the bars (which I'm sure they did as well), the phone is clearly getting better reception than it used to. Speeds have improved, and my little testing so far suggests that signal reception (or processing?) is working much better than it used to.
To add to this, everything else has improved as well. A syncing run with no content exchange is basically instant now, perhaps 2 to 3 seconds total. The entire phone is faster too; typing lag is completely gone, sounds, animations, everything is clearly faster than it used to be.
The improved battery life will have the greatest effect on my personal usage patterns, but then you add higher speeds and a slew of bug fixes and performance improvements across the board. And its free. There's only one way to put it...
This is one hell of an upgrade.
Maury