None of the scenes really grossed me out when I watched it recently, but that's only because I knew what I was getting into. I probably was a little queasy after watching some of those scenes the first time. Yet we never see the crimes being done, only the aftermath. Seeing those murders actually take place may have been a bit much.
Nevertheless, Se7en rides on some great storytelling, gritty direction, and an all-around great cast. One of the things I enjoyed most about the movie was the chemistry between the main characters. This was most evident at the dinner scene as we were introduced to a friendlier, civilian side of the characters played by Morgan Freeman and Brad Pitt, as well as a strong supporting role played by Gwyneth Paltrow.
And I should not forget the classic ending to this movie. You will remember it for a long time as well as the villain, who is played by an un-credited famous actor. You probably already know whom it is, but in the spirit of limiting any spoilers, I won't go further.
All in all, Se7en is just a great flick. It's fun, it's interesting, it keeps you guessing, and it's memorable. The only drawback being that it may not be for the faint of heart.