Thats pretty much the average for hq tabs these days. My Tran gets about 10 hours of hard use before it drains down to 10% or so. I usually use it 1-2 hours a day, leave it on standby with wifi on most of the time. I usually charge it every 3-4 days or so, once it gets down to 20-30%.
What video player are you using? Did you get one from the market or was it pre-installed by Samsung?
Sounds like you got a nice little tab there, good choice for an impulse buy!