Boston is a great location for a Fallout game. It has the history, it has MIT. It has Boston Harbor and thus a chance to expand Fallout into the water, should Bethesda choose to do so. Imagine the possibilities of under water complexes, battles, sunken ships, hidden underwater treasure, and, of course, new water born creatures - mutated sharks anyone? There are also plenty of old ghost stories, odd happenings, strange and humorous events to draw upon in the area to add color to the game. So the setting is a good choice.
The game engine has been updated and the team has more experience with it. They have also, obviously, taken ideas from the modding community and incorporated them into the base game. This bodes well for the game's design, in my opinion.
As to the content/features - I'm not an FPS fan, so the shift towards more of an FPS-heavy nature to the game isn't a big selling point for me, but I know that others will be extremely happy with it and I may come to like it as well. I do like the changes to VATS that I have seen, and I am...open minded...about the changes to the criticals system. I like what they have done with attributes and perks, and the fact that there is no level cap. I also like that they have lowered your starting SPECIAL points. This makes the initial character build more important - but allows you to build on it as you go. I am also a fan of games like The Sims, so settlement building is a huge selling point for me. I also love how everything in the world will now be usable in some way - for modding things, if nothing else. This bodes well, in my opinion, for a decent chance at a fairly decent economy in the game. I also like the fact that the protagonist is voiced. I enjoyed SWTOR when it first launched in a large part because it was fully voiced. I like how companions can be directed to do things for you. And I love that we get to play, however briefly, in the Pre-War world.
Of course, there are a GREAT many unknowns - and because of them, I have to reserve some of my enthusiasm for what otherwise looks like a beautiful game. I think that FO4 will easily surpass the other Fallout games, but...there is always the chance that it will fall on its face. Perhaps it will be bugridden (or, moreso than most games). Perhaps the writing won't be good, or the story will be horrible. Or, perhaps, it will be so complex that modding it will be such a chore that most modders will throw up their hands in frustration and decide not to bother - leaving only the most dedicated modders, and generally tiny mods that do very little beyond changing some textures.
We will see...when we see. Personally, I am hopeful. But only time will tell.