Adobe's Flash evangelist Mark Doherty has posted some stats and a video that shows if Flash 10.1 (in particular Youtube) has any effect on battery life, it's negligible on the Nexus One.
Doherty has a 17-minute long natively embedded video run in the full Youtube site (you may want to skip the first 17 minutes of the video, nothing much goes on). WHen the 17 minutes are up, he opens the Android battery usage utility, which indicates that only 6 percent of the battery has been drained (although the screen does dim out in the video). He also claims that Adobe in-house has tested three hours of H.264 playback over an Wi-Fi connection, which is enough for a movie or two. Even Avatar.
It’s great to see that the newest generation of Flash content can run without making the Nexus One's battery weep juice. Now, we're just waiting for that Flash update to come.