I play op because
1. STEALTH
2. HEALZ
Admittedly, I'm not level cap yet, but I find the Op very solo-able and very survivable. It seems to me that I can do missions on my ops several levels before I can readily do them on my sorc.
Add to that that our ship and our storyline have rocked, and I doubt I'll find another class I like quite so well.
(Also, I like sneaking up and slicing footlockers right under the noses of gold-elites 2-3 levels higher than me. Cackle all the way to the bank... )