It has been over 15 months since my ACL recon too. I have just come back from a few days skiing, which was the first real test for the knee, and it held up great.
I used a brace, more for psychological comfort than for any physical protection. The knee was really stable, and on the 2nd day I had enough confidence to really go for it and not hold back on the speed. No falls, so the knee didn't get tested with a twisting ski situation, but I am not going to force such tests! Did manage to collide with another skier (we were both trying to avoid each other by going over the top and both managed to turn exactly into each other), but no damage done.
I still have some stiffness on the lateral side, although it may be a bit better than before. Had a few incidences of what I think is scar tissue breaking up, but I don't think that process is finished. Still get cracking and popping, and occassional hamstring aches, otherwise no other problems. VMOs just about the same size on both knees, but the upper quad of the left leg still needs working on.