not really, I don't use my machine enough to need one. However, I can sew with my embroidery unit on so its easy to go back and forth, just have to change the presser foot. I think it depends on how often you sew as embroidery can take a long time as can sewing. If you sew everyday and embroider everyday than I would get several machines but if you are like me where its ocassional as projects arise its not necessary. If I purchased the machine I have now as the sewing model and embroidery model separate it would have cost me a lot more, but I think it also depends on what kind of machine you want and your budget

I have a combination machine by Janome and I love it. I mostly use the quilting but find it easy to change to the embroidery unit. I am a beginner to it so still have a lot to learn.

My Bernina 440 is my main machine and I also have the embroidery for it. If I want to sew when the embroidery unit is attached, I usually just get out my featherweight to piece on. It's not any kind of hassle to attach/remove, just disconnect the cable and lift away, but it takes a couple of minutes to also change the pressure foot, bobbin, ect. If I have more embroidery to do I usually just use a different machine.

I have a Bernina 630 with the embroidery unit. I pretty much only use the embroidery for making quilt labels but if I decided that I want to do more embroidery, I would want a separate machine for that. You have to stay close to your machine while it is stitching out and I would prefer to sew something else while the EM is running. It does take a few minutes to change out the needle, foot, plate, rethread bobbin differently, drop the feed dogs and un plug the foot pedal. I tend to wait until I have a couple projects to do before I change everything out.