I used to hate dogs. I was scared of them and would avoid going anywhere were they were likely to be. Then my sister got a dog and I got to know her (the dog, I already knew my sister) and I discovered that dogs are actually ace.
(I had a less profound change of heart regarding musical theatre where I decided that Legally Blonde the Musical was terrible and not my cup of tea at all, until I actually saw it and it was fab).
You?
Most of my ATDs, barely
Liked any of them at first.
Once upon a time I thought people who liked horror films were massive weirdos 
Buying/wearing decent clothes. Never used to give a fuck about it. Now give a big fuck about it.
Running
Hip-hop
The literary merits of The Da Vinci Code
Watched Veronica on netflix last night. Was alright.
Wearing jeans.
As a kid I used to hate them - they felt too stiff and not nearly as comfortable as jogging trousers.
Mince pies and fruitcake.
Didn’t like them at all as a kid. Now, I’ll hoover any up that are left around.
Cheese. Couldn’t stand the stuff whereas now I have an addiction.
i haven’t bothered with it yet! What kind of horror genre is it?
I guess it’s a bit of a ghost story. Reminded me a lot of Under the Shadow (and reminded me how good that film was).
Olives. 15 year old me thought they were horrendous little balls of seawater. Adult me has probably eaten enough to get Greece’s economy back to a sensible place.
Peanuts/nuts in general (used to hate them, love them now)
Marmite (used to hate, now - fine)
Used to go to gigs early enough to see a support band. What a mug.
Same with dogs really. Never hated them but was definitely scared of the bigger ones as a kid (had a nasty run in with a doberman at one point) and the little yelpy ankle biters used to annoy me (still do a bit tbf). Now love most of them and totally enjoy having them lick my face. Two of my friends have labs and they’re lovely. Pretty keen on having a wee beagle.
Also, Vampire Weekend.
Wasn’t that fussed about The Donnas.
Used to hate basically all dance music (techno, drum & bass, house etc) because it was popular among the twats at my school
Got into it mostly after school, without those associations, nice
Tomatoes. Absolutely despised them until my mid twenties. Now I fucking love them.