I don't believe the Bernina 550 has the embroidery - I could be wrong, but the 580 is the embroidery machine. I had a Bernina 180E for 10 years and it never gave me any problems. I also have a 6600 and not any problems there either.
When I wanted to upgrade to a new embroidery machine I tried them all. I bought a Babylock Ellisimo and I really like it.
I think with most high end machines, you have to keep them clean. With the embroidery, they sew so fast, they create more than normal lint - so I clean the bobbin case, etc. each time I put in a new bobbin. Sometimes more.
Everyone is correct - you need to spend some time trying them out.