As for my experience with the GT2, I get between 5.5 - 6 hours of "screen on" time with each full charge.
During this time, I'm connected to my home wi-fi network. My most frequent activities are browsing the web on Chrome, watching YouTube videos, reading news feeds linked to Google Reader (which often involves opening links in Chrome), and using apps such as Facebook, IMDb, Songza, etc.
If I'm playing games, then I switch off wi-fi, but I'm playing games an average of 30 minutes straight (that Temple Run and Jewels Pro are addicting!).
Occasionally, I have Bluetooth active (but usually no wi-fi connection) because I'm connecting a Logitech keyboard and mouse for use in QuickOffice.
At night and when I know I won't be using the Tab for an extended period of time, I power down the unit. I also have the power saving mode permanently switched on, and I don't experience any lag in performance.
CNET's official benchmark puts the Tab 2 7.0 at around the 7 hour mark, but they tested it solely by looping a video file until the unit shut down. I believe they had wi-fi enabled too. Of course, the more you multi-task and the more apps you use, more power is used, and it all adds up in the end.
The reason I gave such a detailed breakdown of my usage is to establish the point that a reasonable estimate is 5.5 - 6 hours of battery life when using the tablet in a versatile but energy-conscious manner. Of course, your mileage may vary.
Hope this helps!