My main reason for getting the 135 was to photograph pine martens, where f/2 really comes in handy, but I have also taken some candid portraits in a poorly lit pub (not really my forte but it worked). I use it mainly on the 5d MKII, but if the light is slightly higher, then it would also work on the 7D in the right circumstances, it just depends on how far away your chosen subject is. Also, while I mainly use the non-IS 100 for macro work, with a full set of Kenko extension tubes, you can get close to half life size and it would effectively be more on the crop sensor of the 7D. Also, the extreme depth of field at f/2 at near macro gives a distinctive appearance, that you just can't get with a normal macro lens. It isn't to everyone's taste, but it opens up a whole new area of creativity. The tonality and contrast of the 135 also helps with the distinctive look.
Basically, you need to decide on your main reason for the lens. Do you want street portraits at a distance lon enough to merit the 135 or macro the most? The answer will probably determine the best lens.