Phenonmenal.
An believeable world brought to life through a compelling story excellently written and conveyed through evocative voice acting. From beginning to end, New Vegas oozes immersion to an unbelieveable level, encompassing a setting of breath-taking wonder, an immensely detailed world. Filled with diverse and beautiful locations you can visit, wonderfully life-like characters you can talk to, interact and kill, mountains of equipment you can pick and use and combine. The gameplay is as utterly satisfying as the setting and story are absorbing. While the introduction of faction karma gives it an extra dimension that FO3 never had. All these factors In combination with the sheer number of quests, NPC types and enemies make it a 10.
It would be perfect were it not for the VAULT system that fails with ranged combat that doesnt work.... i.e. enemies close range too quickly and also issues with game balance at the later stage of the game, where skills are just maxed out, especially if you have strong party. In some missions cant be completed because of an action or lack of action not taken earlier on, that the PiP boy did not warn you about.
Strangely enough there are no minor issues with the game, except maybe the issues with spawning enemies - to close to you.
That I aside with all the content packs this game is worth a ten, even with all major issues.