Hmmm, this is interesting. For me, panning problems is the least of my problems. I do a "quick mix" just with pan and volume first, on my monitors. Then I switch to mono for EQ, compression and other effects. My problem is that my monitors (M-Audio 5") have an extraordinary lack of bass response. Basically, I've learned that if the bass is weak on my monitors, it's good.
I usually switch to my computer speakers (Logitech 2.1) to finetune the bass.
And still, the bass (kick and bass guitar) is never nice and tight and clear as professional mixes.
Basically, I want a good way to mix the bass, and thought mixing on headphones might help. I still test on my computer speakers (with and without the subwoofer on) and in my car and on my bluetooth speaker and laptop too, but can never get the bass sounding really tight and clear.