I've been playing this for about 2 days now and I have already been very impressed. There a some bugs in it, cause a little freak mode but very very little compared to the older Fallout game. I've only encountered a bug once.
Other than that the gameplay and voice communication is dead perfect. Many of the enemies move different and feel so real compared to Fallout 3. And even have a bigger range of enemies. Even the Deathclaws have 8 different types including the new Chameleon which makes your fight alot more interesting. Weapon and Armor mods constructing does take getting used to it. But once you do, adding one will be very simple to do.
You can also make many settlements and use their places to help store all your items you carry and even store your Battle Armor, in which you get this very early in the game. You can easily repair, scrap, and fix the town up. Takes plenty of time, but on your off time can go do missions and easily get the supplies you need.
Level upgrades only go throw perks now instead of adding points which is not really a bad thing. Makes things a bit more mind thinking and planning to how you want your character to be. Of course one simple boost off a Pistol perk and such will definitely make an increase on your combat skills as if you're level 5 times at once.
Overall I think this game definitely a winner with a whole lot to come later in the DLCs. Enjoy your time in the Wasteland people and have fun creating your settlements too.