i personnaly believe. if it aint broke dont fix it. fallout 3 had a good formula and obsidian has fine tuned enough to make it even better. i hope its not reviewed badly
First of all, what you are saying is a gross misrepresentation of the first law of engineering; if it isn't broken, don't break it.
A more accurate representation of the notion you are expressing would instead be; "If it isn't broken, don't ever try to improve upon it!".
If nobody ever took any steps to improve considerably upon something, we'd all be stuck in the stone age.
Now, if it turns out New Vegas is simply more of the same, then it will get alot of flak for it, and that is how it should be. In that case, Obsidian would be doing exactly what they did with KotOR 2, that is capitalize on the success of another studio without adding anything new whatsoever, resulting in a game that was [censored].