The FA135 is just very easy to take along and isn't obtrusive. Actually, that's everything the Tokina isn't :G.
Now I understand what you were saying. Actually I can fit the camera and lens in my pocket. When the moment came, I could yank it out and take pict within 3 seconds. Very handy and mobile indeed.
I have FA100 2.8 Macro which is even slightly longer than 135. Before the Easter Parade I was pondering what would be the main lens that will be at the DL . I picked 135mm because of that. The other lens I took was a wider FA28mm2.8. At the end of the day I did not even use the wider 28mm as I was so busy.