Heres what you need to know if you want to have fun with this game:
Bethesda has [censored] y writers, so dont even try to make sence of the rediculous plot holes and crap in the main story, Just play the mq it for what it is, a non-sence story with bad writing,but(if you can get past the first part,which I have troubles doing) fun never the less.
I have mixed opinions of combat in this game.
The best part about the game is the map. Once you go through the crappy subways and find fast travel points in all the "zones" of DC, the city is a blast to explore(especialy if you have seen the monuments irl). The rest of the wasteland is very fun too, definately focus on exploaring in this game.
OR.. buy FONV. It has a decent map(though not as good as FO3s map, but close enough for the game to still outweigh it imo), a good,4 sided MQ(that makes sence), better crafting, better companions,better weapons/combat(aim down sights is a BIG plus), and more.Plus, if you get all the dlc for it, you are in for a story arc/moral lessons that are amazing, and makes the game seem like more than just a game.
Just my two caps. FO3 was very good, but NV is better in allmost every way(IMO at least).