So, there's one show that's a great(ish) example of one that I thought I'd hate but then ended up loving. And that show is GLEE.
Now, by now, you guys should know how I feel about Glee. I have a love/hate relationship with it now, sure. But when I first started watching the show on Hulu, after all the hype and the HUGE ads, and the promise of Jane Lynch, I was ridiculously disappointed. I felt the characters were complete stereotypes (the footballer, the theater geek, the gay kid, the black diva, the cheerleader) and I could not stand the auto-tuned voices of the singers.
However, for some odd reason (I attribute it mostly to Jane Lynch, though she's surely not the only reason), I kept going - I kept watching episode after episode. Until, finally, somehow, I fell in love with the show. I couldn't wait until the next week's episode and that season finale just left me hanging on the edge of my sofa.
Even though I rant about Glee a lot, I still quite love it for some inexplicable reason and compared to the hatred I had for it near the beginning, it's really redeemed itself.