I used to allow printed/photocopied cheat sheets, but too many students were including reduced photocopies of complete homework solutions, lecture notes, and/or old homework/lab/exam solutions, or just photocopying cheat sheets created by other students. (The most extreme example I've seen consisted of 144 pages of notes and solutions — four 6×6 grids of reduced pages, one on each side of each sheet of paper — none of which was actually readable by normal human eyes.) Those students performed significantly worse on the exams than students with their own hand-written cheat sheets.
If necessary, we will offer a makeup exam early next semester for students who miss the final exam, either with or without an Incomplete. Please ask Jeff for details.