Are there any phrases or idioms to describe someone rejected the chance to do something at first, but liked it the moment they tried it?

Solution 1:

Watching the movie after initially disliking it, I immediately came to appreciate its greatness.

Watching the movie after initially disliking it, it's greatness immediately grew on me.

From The Free Dictionary:

appreciate: to recognize the quality, significance, or magnitude of

grow on: to become increasingly liked or appreciated by you

You could also say -

• You can come round to their point of view (i.e. change your opinion).

• You can also take a shine to something (not just people).

Solution 2:

to blossom forth TFD an idiom

• Lit. [for a plant] to burst into flower. All the trees blossomed forth at the same time. Each spring my tulips blossom forth in all
  their glory.

• Fig. [for someone or a concept] to develop or grow quickly.

As in:

He accidentally joined a football match one day and his interest in the game blossomed forth.

And for John's reply to the event unfolding:

John says to Peter: So, I see your interest in football has blossomed.

Solution 3:

Despite: He had a great time, despite his initial pessimism.

Or, "The pie was good, despite the first, last, and every slice in between." (added for levity)