I used to have terrible problems with Eclipse on my MacBook running OS X. Editor text was bouncing up and down and all my lines were squashing. Have a look at the photo if you think I'm crazy.
Finally I have managed to find out what has caused this behaviour: It is the font size, which was set to 9.5. I'm not sure if the small size or the .5 bit that is to blame but but as soon as I set it to 11pt everything was fine.
I'm happy I found this because I was very short of changing over to XCode.