I gave up after Chapter four, didn't like it.
yeah its either something you like or dont like, theres not really a middle ground especially since the chapters are long...i love the fallout universe in general though so i was easily addicted to it, but pretty much every fanfic ive read has gotten me hooked quickly as long as the story is good
I love Fallout, just not that fic.
you mind if i ask what you didnt like about it? im just curious
Well...more-or-less everything.
Didn't identify with the characters, felt the universe was far too grimdark for ponies, the writing style seemed to drag with too much description pasted on everything, Little Pip has all the attraction of wallpaper paste on cardboard, it didn't capture the sadness of civilisation ending like Fallout itself did, the sub-plot with the mane six's terminals felt kinda tagged on rather than well integrated into the fic itself.
Didn't identify with the characters, felt the universe was far too grimdark for ponies, the writing style seemed to drag with too much description pasted on everything, Little Pip has all the attraction of wallpaper paste on cardboard, it didn't capture the sadness of civilisation ending like Fallout itself did, the sub-plot with the mane six's terminals felt kinda tagged on rather than well integrated into the fic itself.
through the first couple chapters i would definitely agree with you, it gets a lot better though...but im not trying to sell you on it i was just curious 
Eh, "it gets better later" doesn't really sell it to me anyway. A story as punchy as Fallout should grab you straight away.