It will be painful at first if you don't naturally have good ears, it was painful for me (which is why I avoided doing so on saxophone), but the payoff is huge. It changes you as a musician. I've heard songs on the radio where I knew the chord progression and thus knew how to play the song before even picking up the guitar, that is pretty cool. I might come up with a bit of a song in the shower or in the car and when I sit down at the guitar and figure it out. Neither of these would be possible if I hadn't put in the hours listening to bits of songs again and again.
At the same time, if you are a beginner or intermediate player, I'd recommend justinguitar.com to get started. His youtube channel is extensive, and he and Marty Schwartz were my two main guitar teachers.
Also, I've met people who have played guitar for some time but cannot play bar chords. This simply shouldn't happen. There will be a song you want to play where you will need a bar chord, and you will either have to learn how to play bar chords or learn a way to "cheat" on that particular chord. Bar chords are awesome, piano players would kill to have a movable shape that makes transcription trivial (they'd also kill for a capo). They are well worth the initial effort and once you can finally play them you'll realize that they aren't that hard.