I wasn't really expecting a huge jump in performance but the GPU performance was something I was waiting to hear about, that sucks due to the hype that was built around it. Now I'm not even sure on battery life just due to how much power the display takes from the rMBP. I mean I'm sure will see an improvement but not the huge jump everyone was expecting. They need to improve battery tech or find a screen that has better power consumption.
Well, I think the big thing is supposed to be better power management. From what I've read, computers are idle for the vast majority of the time and there are a lot of wasted CPU cycles during times like for example, just simply writing this post. It takes an extraordinarily small amount of the CPU's processing power to allow you to type and most of the CPU's processing is wasted (thus wasting energy) during these moments.
Ultimately, the real world test is what is going to matter. If a Haswell Macbook Air or Pro can last 8-9 hours with real life usage, I think it would be considered a success. 10 hours would be astounding and I would be snapping up some Intel stock.