I have been playing around with the GM for a while now on my MacBook Air. This far, I can say that the Flash player hogs memory and makes the fans go wild under Safari 5.1. This means that I will be using Firefox until ClickToFlash comes up with a compatible release.
Initially, a daemon named helpd ate a lot of the memory first couple of times I used OS X Lion. It paged in nearly an entire gigabyte of virtual memory in a few minutes and the fans went up to full speed. But I forced the process to quit, and helpd has been calm at all subsequent reboots.
With Pages, Firefox and iTunes, 25 % of the battery capacity lasts for 80 minutes, so it seems like I get 5:00 to 5:20 hours on a full battery charge with this usage. This is what I used get to under Snow Leopard as well. In other words, I can see no significant change in battery life under the circumstances.