If you have good headphones, I reckon you can hammer out a fair bit on them. I've got some fancypants Bose ones, that really do give an amazingly accurate version of whatever you should be hearing. Of course they are still far from perfect, so all the fiddly bits go through monitors and everything, but the headphones are good for throwing ideas together and sort of mapping out tracks and the like. I'm hardly allowed to make any noise at all (neighbors are ****s) so I probably do as much as %50 of my stuff on the headphones, and save the volume for tweaking the sounds just right, and then stuff like EQ, mixing, mastering...