If I were going to purchase, I would want a separate machine for embroidery so I could keep it set up and working for me while I would be piecing or quilting on another machine. I personally would also consider a separate machine for quilting -- a Juki 2010 with a 9" bed or, if I could afford it, a Sweet Sixteen sitdown (about $5,000 if you can find one used).
For piecing and machine applique I love my Bernina 1230. If I were to replace her, I would be looking to add some additional decorative stitches (especially a curvy feather stitch for machine bindings; my straight feather stitch is not as good because wobbles show up) and possibly a needle threader.
My experience is that a combo unit is unlikely to perform all of the different sewing functions (piecing, embroidery, quilting) equally well. By buying more specific machines, I expect better performance for each function plus less complexity in the engineering (so fewer trips to the sewing machine doctor).