EDIT: By the way, the vandalism set (7833-7843) now has a new case, 7835 has a scratchitti'd window. These things are getting beat up FAST! 7844-7854 has brakes that don't sound normal, rather a bit intense/screechy.
Actually, when 7860-7870 was still new, I got to ride on 7865 and 7866 by luck twice. On one of the G/O's where trains terminated at 74th Street, I got off 7857 for the next train going to Queensboro, and got on 7867. Then I kept seeing that set for a few more times, until I didn't see it much again.
My goal is to be on every end of a set, so here's my progress:
7811/7821: Done
7822/7832: Done
7833/7843: Still need to be on 7833
7844/7854: Done
7866-7870, 7860-7865: Done
7855-7859, 7871-7876: Still need to be on 7855, although I have been on 7857.
7877-7887: Have never been on it once, although I did have an opportunity to get on 7877.
7888-7898: Done.
7221-7230: Still need to be on 7221.
7231-7240: Haven't been on it yet, though I did have an opportunity to get on 7240.
7241-7250: Still need to be on 7250.
Not to sound too much like a foamer though!
Going back to 7860-7870, I've been on that set 3 different times and I have seen it many more times.. though it was said that 7868 had stuck brakes/dead motors making it screechy. I heard it myself seeing it once, but I'm not sure if it's OOS due to that reason.