I'm not sure what level you guys are at and I don't want to assume you're beginners in case it's wrong, I'll just say that I've been a trained musician for 21 years and a guitarist for 14 and I still can't get the right chord every time straight away, although it's interesting that you mention this because I recently impressed someone when I was playing her some music and had a guitar handy and said 'I've never tried this before' and got it almost straight away, and after I'd done it she almost didn't believe me when I said 'It's really not that impressive, I just got lucky that it's the kind of melody and chords I'm used to hearing.'

That's all I think getting chords by ear really is. Some bands I've listened to and learned songs from tab so much that when I hear something I don't know I've got a pretty good idea already and it's just a matter of finding the right key. Other stuff I've listened to for years but if I try to pick up the guitar to it one day I'll wind up thinking 'What the **** am I doing?'

If you can't get something by ear don't be afraid to use tab. I've never listened to anyone who said it was cheating. It's a time saver, but I never saw it as not learning. What I used to do by tab I can now do by ear, and anything I do by tab now will end up the same as long as I keep revising it.