So, Fallout 3. For people who have played any of the Elder Scroll games (especially Oblivion), you know what to expect, huge areas to explore (in this case a nuclear wasteland version of Washington D.C.), one main quest with lots of smaller side quests, mini-quests, and ongoing tasks, and a whole lot of characters to meet. Lots of people describe it as Oblivion with guns, and this is essentially what it is, but with a lot of extra little things thrown in to give it a little spice.
The main extra is karma. This is how the game gives you so much freedom in the tasks you are required to do. Do you want to help the misunderstood ghouls out by convincing people that they aren't that bad? Or do you make them pay for their discrimination by removing their heads in glorious slow-motion (I'll get to VATS shortly). Or do you discriminate against them too, and wipe the melty-faced creatures out? It's entirely up to you.
But for a cost. Kill too many innocents and your karma will pay the toll. This actually affects the gameplay, everything from being hunted by bounty hunters, speech options, and how other bad-asses will treat you. It even affects the radio stations, with reports of your shenana... shennann... rampages (Porky Pig moment there) being broadcast, warning people about you like some sort of boogyman. This alone will provide heaps of replay value, as people who play 'positivly' the first time round will inevitably want to taste the dark side second time round.
Now, the combat. This is where mostof the issues arise. Fallout 3 may look like a shooter, but it does not play like one. Unleash on something with an automatic weapon like a chinese assault rifle, and you'll likely empty a clip while maybe making contact with two or three rounds, as you see the rest veer off everywhich other way. Even with sniper rifles it's difficult to get a head shot, especially on a moving target.
This is where VATS (Vault-Tec Assisted Targeting System) comes in. With a tap of the R2 button, time freezes, and you can select a target to aim at, complete with hit chance, and the hit points of that particular area. The hit points are important, 'kill' the arm that's holding a gun, and they drop the gun. Take out the legs and they can't run. And if you kill someone/thing with a VATS shot, you get to see the whole thing in slow motion. I'm still loving turning heads to goo in slowmo.
So basically, if you loved Oblivion, or the style of game that Oblivion is, this is at least worth a look. You can really get as much gameplay out of it as you want, with plenty of quests and strong replay value, as well as (eventually) some DLC available. But if you're looking for an RPG shooter, you may want to wait for something like Borderlands to be released.