I have a Bernina 640 with some goodies that I simply love. I can tap the foot control backwards (with the heel) and it will do needle down/up (or half of a stitch, in other words). The many feet available is a dream come true. The knee control to life the presser foot is wonderful! Although when I switch back to using my 201, 15-91 or the Belvedere Adler I do forget that their knee control is for power!
Still... it's such a pleasure to sew on the old gals that sometimes I can't make up my mind which machine I want to use! I keep my 201 in the living room to watch TV as I'm piecing. The 15-91 sits in the entry way, stored there for when I need a "tank" to sew leather, and my Bernina is in the sewing room with the Belvedere Adler. My Tin Lizzie is in the quilting studio and my Wilson and Wheeler keeps it company.