I am personally playing Fallout on PS3 atm. I should have the money by the end of next year to build my own gaming computer which will, no doubt, be overkill for fallout but hey, whatever. And honestly you shouldn't struggle without a controller because a controller makes the aiming very stiff while a mouse makes aiming feel much more smooth and free.
I recently built a rig and am planning on playing Fallout 3 and F:NV on it. However, I have not played a real (not browser based) game on the PC since the original Doom. I am so controller-indoctrinated that trying to play with a keyboard and mouse feels as foreign to me as trying to drive a nail with a monkey wrench.
That being the case, I grabbed a wireless receiver for one of my 360 controllers and am planning on using one of those.
I am looking forward to the ability to mod, better graphics and running at a higher framerate, but I am not looking as forward to gaming on my 27" monitor as opposed to my 55" HDTV with 5.1 (and my comfy living room chair).

This then frustrates me and makes me worse.
I played hundreds of hours of vanilla FO3. It's good to be able to take a high level character and use mods like increased spawns, running into armies of Super Mutants for some mindless, dangerous, Blood Sample collecting crazy action game-play. For giggles. Mods are fun, and the community is so vast you can pretty much find one for everything you think of, and they also add crazy longevity to a game and its community, which is why Beth supports modding. 