I bought this Game just because it was cheap while i was in London. I loved Fallout 3, but i wasn't sure about the Vegas/Cowboy Setting. Well, after finishing my last Game i just wanted to give it a try.
I played for 4-5 full hours without even a break. I didn't even noticed ;)
Later i found out i had made some little misstakes in my charbuild so i had to startover after already playing 30 hours! And i wasn't even mad about it!
Now my new char has already 60+ hours on the new save. With 2 other "branches" with each also 5 individual hours. So i already played around 100 hours without be worry about it.
I just started my third and final char. This time i will just play the main quest line for the last group that i haven't finished. But i'm playing on hardcore this time and STILL it is FUN! Its not really Hardcore, but it's lot harder then normal. You have to take a look onto food, sleep and water while also beeing forced to not carry to much. I think it will take me another 10-15hours to have this finished.
So in total: 100+ hours already with maingame and one DLC. Still missing one brance of the mainquest for another 15hours.
So... about 120+ hours is NOT what i would call "just Fallout 3 with a little new story"