What brand/make and model do you have? Janome 6600
Which features do you like best? The range of fancy stitches. In fact, that's all I use it for, since I also have a 1600P I also like the separate bobbin winding motor and cutter.
Use the most? fancy stitches, thread cutter, needle threader, start- stop (I don't use the foot pedal at all)
Which features do you NOT use? knee lift. I have bad knees, so this is no help.
What I DON'T like is the tendency to blow fuses when I am working at speed and make an error. A trip to the dealer is 150 miles. It works just fine if I do.
Would you buy that particular brand/make and model again? In a flash. I have a 6600, a 1600P C, which is my straight sewing work horse, and a little portable, used only for classes. My Janome dealer is a gem. When I have had questions, he or his staff take the time to work them through on the phone or in person. I have been a fan of his for 9 years, since my TOL Bernina lemon died after 3 years of use and good care.